Yes, It is possible to get contamination from DMSO. Just culture the DMSO with the media in a petri dish culture it and look for contamination if you have some DMSO from when you prepared the stock. Alternatively, you can try to filter the DMSO or whole freezing medium before saving your cells.
If you want to revive these cells and have some other vials try a range of antibiotic mixes as you revive them, and later you can wean them off. You might have to select an antibiotic cocktail depending on which cell types and contamination you see.