After some more tests it happens that if textures are enabled the game is only 10% slower to load, so I have decided to re-enable them by default, I might add an option for this in the option screen later.

Without textures:

 

With textures:

With nothing at all except lights. Ok, this one is pretty useless, but I got it because of some glitches and thought it was nice to see how lights were working (the map is plain white, but because of lights there are some colors/darkness)