Any mesh over 20k
tri's will usually crash the program, don't mistake quads as your face count, 4096x4096 is the dx9 maximum for textures. Any texture larger than this will simply be reduced by the engine so it's pointless. I reckon all 3D game engines display textures at around 72-100 dpi (otherwise= bad performance and memory consumption) so any res higher than this wont be noticed and again probably reduced. I haven't tried anything larger than 2048x2048 in Reloaded yet.
Edit* Just remembered, I did use 4096x4096, worked fine, at least in an older Beta
Tip*It's best to tile smaller textures on very large entities, if you really must use 4096x4096 your normal and spec maps don't need to be the same scale as your diffuse, so reduce these to save on file size.
I have created models as large as 400 feet in 'real world' scale terms and not had any issues with it in Reloaded, I believe they can be a LOT bigger but yet to test it. Of course if your model is larger than the world size in height or width you will have problems.