Hmm I guess if you have enough money, and make the artist feel like he's getting his worth and not scammed, you could do anything.
Some are more than happy to do your ideas if the price is right for them. The time-frame and pricing depend on the artist though.
Look for artists on several sites like ArtStation, ArtistsnClients, Pixiv, itchio, Twitter, Instagram, etc. and send every suitable artist you like, a scripted message with your offering. See who wants to cooperate.
Also: Does it have to be the same artist for all 30 images? Only pick those who you feel are 100% willing to go all the way through. The higher their salary will be, the more likely they're willing to stick for the long-term. I have no idea about contracts though. And big companies will probably demand unreasonable payments, but I'm not sure. You could still check them out too.
When asking for art, include as much detail as possible. Is background included? What kind of pose for each drawing? What colors? What feel does it give off? Etc.
DISCLAIMER: I'm no expert. I'm a beg-artist who got ripped off once and "only" sold one NFT for 20 bucks lmao. But that's my vague idea of this whole business.
Anyways, good luck with your project. :D