The way the engine works is that it draws 512 double sized pixels in every tile. Say I wanted the resolution to be 5x5, it would draw 25x512 pixels on the screen before doing any raycasting. It isn't as slow as most people would think, since I don't create it on the map, and just put it on the screen.
Well, that was a mighty fine attempt. Textures work by reading a multi-dimensional array, so I can quickly reference the colours of a texture datum.
Since I could do that, I added more colours, and made more textures with different colours!
Also, I could add letters to the texture walls. Very fun. =P
Fun, fun. There's only one problem which I can't pick down. When I move (not turn the direction), a majority of the pixels flick black for a few seconds, making this wavy pattern in every tile.
Anyway, this was a fun day. =D
[edit]
After a while of work, I put in floor casting. Now the ground has textures!
Does it draw the map based from a dmp? If it's so fast as you say, you could build a proper game.
Just a suggestion for your current problem, couldn't you add all the 'new' pixels to a list, then set client.screen to the new list? If this is what you're doing, or you don't use a client.screen based system (though it sounds like you do), please ignore me. Don't worry, I'm used to it :-P.