My tiles are messed up.

[D4rKv310c1ty]

Hey there, I need help with my tiles, I was creating a nice big level something to do with a dark, evil magician taking over a village and I was introduced by a friend to a server anemd 'Perilius' and 'Futura' I visited them and then when I went back onto my graal level editing program my tiles had messed up, chairs looked different sand patches dirt detail everything was different, how do I reset the tiles back to default?