Can you tell me a bit more about the engine?

I am considering either rewritting my graphics engine or 'adopting' someone elses.

My maps have 2 layers, 64 x 64 pixel solid background tiles, and 32 x 32 pixel transparent tiles. There are 32 different flags per tile, we can also assign music and sound to specific tiles. Max map size is 1000 x 1000 tiles. 2 layers isn't really enough Client is drawing 1024 x 768. The map is buffered by drawing the visible area +2,-2 of each tile in all directions, this allows nice smooth scrolling and means that we have to draw only 1 row / column of tiles at a time.