[amonrabr]

You can use, addtiledef2 image,levelname,x,y; .. to replace an image (any size) in the tile.

or "addtiledef image,levelname,type;" to replace all the tile...
If u wanna replace the pics1 using the same kind of floor use type 0, if u wanna (example) add more chairs, use type 1.
To know what kind of floor is for type 1, look at some examples in /levels/tiles (if u have, look at tile_inside.png)