[DustyPorViva]

Well if I recall, Era's tileset is a 24-bit, not 8-bit, PNG. The level editor can not read 24-bit PNGs, and what you're looking at is usually the sign for that.

Also, please provide a second deliminator when using addtiledef:
addtiledef image,LEVELPREFIX,1;
For example:
addtiledef image,mylevel_,1;
addtiledef image,myeralevel15.nw,1;

Something... without providing the prefix for the level, it will add the tiledef to every level offline. That's annoying when you show your friends and let them try out your level only to have it mess up their default tiledefs as well.