I feel your pain. I've been SUPER picky about what I use in my own work. Half the time I'm finding that EVERYTHING made so far is either not what I want, or not EXACTLY what I need. I've ended up making quite a bit... especially lately.
Texture work is pretty easy outside of PLT's (which I'm learning to loathe). Tileset reskinning is sometimes very easy, sometimes very hard. Depends on the tileset. Most of the city tilesets have a lot of different textures. They're also used all over the place. Sometimes it can be very hard to get it perfect. You can retexture things to look like Skyrim-styled textures, but it's still not going to look the same in NWN that it does in a newer engine. However one 256x256 texture is the same as another 256x256 texture. You can detail those up to high heaven. Even the worst models out there can be made amazing with great textures, and the best models ever made will look like poo with a poor texture.
Just look at these two for minecraft. Which do you think is going to look more realistic? (not that minecraft is realistic anyway)
If you want to get into it the main hurdle, aside from learning how to make good textures, is the DDS file format. It can be a hassle. And those times when it flips the image... ARGH! I swear it happens sometimes, and doesn't others. It's a bloody conspiracy!