Why don't you make your own characters? If you used these guys for anything you would have copy right problems. You have a fun style, but you should make original characters instead of this crossover fan-art stuff.
Oh, these are just for fun and practice, i'm not really intending to do anything with them or make money, so i think i'll be okay with the copy right things. But i have a ton of my own characters actually, ahaha they outweigh my fanart. XD