looks like misnamed file to me.
might not necessarily be a texture though, if you created any new decorations, enemies or pickup sprites last time you had your project open, it could possibly return the same error if its looks for the first frame of animation for that deco or enemy.
go through all your folders, look for non-alphanumeric characters, if you cant find them, back up your .dat files, erase everything in maps.dat, then start with deleting stuff in enemies.dat first. see if it loads, if it doesn't then enemy isnt the problem. proceed with decorations.dat, et al. when you find the one that getting rid of the stuff in it allows the project to load, then you know where your problem is and you can do a throrough check of those images to find the one that is misnamed. get it right, replace dat files with your backed up ones, and you should be ok. the technical term for this process is "deconfuckulating"