Glow Slime: Not very good, especially since both Formula Synchro and your very own Flame Slime are much better
Flame Slime: Better/on par with Formula Synchron. Since there's no Bulb to abuse, it's actually OK.
Moss Slime: Not very useful; You could perhaps make it a Tuner to make it up for the lackluster effect?
Aqua Slime: Themed Librarian. Not bad.
Swamp Slime: Now THIS is broken. It can easily be summoned by a Junk Synchron, and lets you immediately thin your Deck by 2 cards (3 if you summon a Formula afterwards), with no costs whatsoever. Maybe you could restrict the monsters that are summoned, but you should definitely do something to make it less generic; as of now too many decks can abuse it.
Slime King: I believe you have some sort of combo for this card, since it is pretty generic as of now. It has a pretty powerful effect, but most of the time you should be summoning Quasar anyway. =
Otherwise, the arts are pretty cool, but I believe you could add something to make your cards a bit more unique, Outlaw. Cool cards, btw, dude.