The motherboard is server-sized, not ATX-sized, it won't fit in a consumer case.
I would suggest an ATX-sized board.
If you're going to run linux as main OS, are you sure you want nVidia graphics?
A 2011-CPU isn't necessary if you're just going to do stills editing. It's a good thing for video rendering, but you didn't mention that. Of course it's also a good choice for virtualization, but if you're not going to do video rendering, you can save a lot of money by going for either and AMD system with a lot of mobo functionality if you need that (internal RAID solution for data redundancy for instance, but if you're taking a lot of pictures I would expect that you would have an external NAS solution, but you have put a lot of HDDs on your list, so maybe you need the extra SATA ports and functionality of a high end AMD board, just look into it, a lot of the value proposition of the AMD platform comes from the full-featured AMD chipsets and mobos, this is much more compartimentalized in Intel's product portfolio), or by going for a "business" line Intel mobo with a 1150-CPU (which will typically game a bit better and will be cheaper). Since you're only going to use one GPU card, a 1150-board will typically offer enough bandwidth. The non-k Intel CPUs are still a bit overclockable on some mobos, and have VT-d, whereas the k-versions are not that well overclockable (for paying premium for them and sacrificing the most important functionality, VT-d), so a non-k CPU is definitely better on the 1150-platform. Another benefit is that you can get an 1150-CPU with iGPU, which makes a lot of sense if you plan on running Windows virtualized.
Since you need a lot of storage space, linux with windows virtualization is probably the way to go, as Windows can't use more than 2 TB of those 4 TB HDD's, and linux has SSD caching for HDDs, which would offer a considerable performance benefit.
Depending on what version of Lightroom you're running, I would recommend running it in linux with wine. It takes some tweaking and downloading a few windows-dll's from the MS-KB, but it works just fine with most Lightroom versions. I would definitely do the photo management in linux with Digikam, it's by far the most powerful photo management software and saves a lot of time. You can even search graphically, for instance, if you have a photo of a windmill on a green field against a blue sky, but you don't remember where you've put it, you can draw a crude windmill form in black lines, put a blue line on top and a green line underneath, and with a plug-in, Digikam will find the windmill photo for you, and it works pretty fast and precise. The geo-tagging and keyword-tagging features are also way better than any other program, and the file management of course is linux-based, so much faster, safer and more efficient. You can bind GIMP or Darktable or Lightroom in wine in Digikam for switching to photo editing. Digikam is made for Qt-based DE's, so that means KDE mainly. I would definitely recommend SolydK if you're looking to stick with Ubuntu (which I would not recommend as such), because it solves a lot of Ubuntu problems and has a nice KDE implementation, or even better, using OpenSuSE 13.1 instead of Ubuntu, because it's next to ROSA probably the best KDE implementation out there, and has a lot of advantages in that it is really easy to use and has a central system config/administration GUI-application. OpenSuSE is incredibly user-friendly in the KDE edition and also very stable and quite fast for a KDE-centric distro. And of course you get the added quality of the RPM-software packaging, the suse build service and the Yast 1-click install feature. Another big benefit of OpenSuSE is the integration on Xen virtualization, which paravirtualizes better than kvm, whilst not being as detrimental to the system as Oracle VirtualBox or VMWare (which always lag behind on kernel modules compatibility, there is just often breakage if you use these). If you want to use a PCI passthrough for a Windows container, I still recommend the plain open source kvm-qemu virtualization with virt-manager, because it's the easiest tool for the job and kvm-qemu causes the least breakage and has the highest performance without full hardware virtualization. If you want full virtualization (whereby the hardware of your computer is not accessed directly in any way by the guest, but the guest "sees" a completely virtual hardware part, for instance a graphics card), go with a commercial solution like Xen, VirtualBox or VMWare, because kvm/qemu does not offer powerful full GPU virtualization, if you want paravirtualization, go with Xen, it's the better solution and the code is more open source than virtualbox and vmware, and if you want hardware passthrough, go with kvm. If you want to completely virtualize the CPU, also go with kvm/qemu, qemu is by far the most universal full CPU virtualization tool.
For gaming in Windows, PCI passthrough just performs great, but it requires two GPUs, so at least a CPU with iGPU and a single discrete GPU, or a CPU without internal graphics and two discrete GPU's. If you're going for single-GPU passthrough, which is called VGA passthrough, your choices are more limited, and it just doesn't work with nVidia GPU cards, and it's a hell of a lot more difficult to set up, you basically need advanced linux skills. VGA passthrough works well with kvm and VMWare ESX, and works OK on bleeding edge distros with Xen, but doesn't work with other constellations. For VGA passthrough, I would also recommend only using enterprise grade distros, i.e. CentOS/Fedora, OpenSuSE, ROSA, Debian and Arch, and keeping a tight and clean system.
Based on what functionality you want, you can save a lot of money on your hardware without losing performance.
I would definitely also recommend Samsung SSD's. As a rule of thumb, Sandforce controllers or other controllers that use dedup/compression to accelerate the SSD performance, are not as good for linux, because normally you would fully encrypt your disks in linux. Samsung SSDs use hardware encryption, and do not compress, encryption doesn't influence the performance of the SSD at all. Also, the Samsung hardware quality is pretty amazing in general.
You will need a bigger power supply with that class of GPU and so many internal HDD's and such a CPU/mobo. An 850 W PSU will have to run in the upper range of it's capabilities the whole time, and that will make it annoyingly loud, and since you've opted for an R4, I suspect that you don't want loud.