This is a concept of a possible in-game tool that would allow creation and upload of TF2 war paint skins.
Everything you see here is concept art created with the purpose of imagining how this tool could look and function.

The war paint system that Valve has created is very flexible and allows for creation of very unique and beautiful skins. However, the war paint creators were not really provided with necessary tools to realize the system at its full potential. Most never go beyond simply replacing textures of already existing skin bases, and if a creator wants to make something more complex they have to edit the proto_defs code which is not easy to get into, and Valve does not add custom coded skins into the game.
Some sort of tool and acknowledgement from Valve are needed.

KayEf — Idea and graphics.
Jacov — graphics.