Abdielord93

You're welcome.
Just a few more additions:
1. If you buy a Core P3, make sure you have enough space in there (it's smaller than the P5).
2. Do not think you can use the included riser cable - it cames with a (nearly) 180 degrees bend. And it is not working, at least mine did not. (I'm honestly not sure if that is a result or not). I've seen some people claiming that they got a working one, I (sadly) did not. And I'm not the only one (search Google, there are not only a few). I bought another one (EasyDIY X16 25cm for 30 bucks @ Amazon). It works perfect (as far as I can tell).
3. Make sure that you do not want more than 3 2,5"/3,5" HDDs or SSDs (more won't fit out of sight).
4. Make sure you don't want a DVD or Blu Ray disk drive; It has no 5,25" slot.

Whatever you use to attach it to the wall, make sure it is able to hold your PC. I (for example) use a TV mount which is capable to old up to 100Kg even considered the fact that the weight of my PC is about 20Kg. Remember: You are going to hang a lot of money on the wall. Do not try to safe a few bucks on your mounting or it may cost you many more...
 
I do not use a self made case (I'm not able to made my own ), I use a Thermaltake Core P5, so I'm not able to give you advice how to build one (at least no experience based advice).
I also would suggest to go with a custom loop - do not use air cooling if you have no airflow. Trust me, it will raise your temps - not only a few degrees...

Inspiration (if you have a large budget and creativity)
 
 

I would recommend doing a custom loop and doing away with the case for max aesthetics(assuming you can afford it).

you sure you dont mean PCIe? PCI is kinda outdated and mostly gone

When I was planning to build a ITX gaming pc, i was thinking in the V1 and bitfenix prodigy ITX, both looks good, but the V1 its too small and you cannot put a 240mm inside I think...
and the bitfenix, you cannot see your system inside GG, I was planning to switch to the NZXT MANTA, but today I buyed two SP140 for intake in the EVOLV, and the difference is juge!!
almos 10ºC drop.

Im using Noctua NF-A14 IndustrialPPC IP67 2000PWM. They are ok-ish in noise up to 900-1000RPM. (cant really recommend going higher in RPM with those)
I also have Phanteks PH-F140SP fans. They have about the same noise but cool a little bit worse at same RPM. 
 
Both have a "hum" noise, regardless of RPM. 
 
I wouldnt really recommend any of those if your not planning to use them at maximum 5volt. I hope they are still better noise to rpm /cooling fans. Im thinking about trying out the maglevs.