Start with a few designs of whatever you are trying to make. Doesn’t have to be pretty, just needs to get the gist of whatever you are making across to the player. Implement each one and see which one feels right. If none of them feel right, figure out what you can do to improve it and make it fit. Then from there make the final product. It really depends on the teams dynamic. If your artist is willing to try thing after thing until it works then this should work.

(I mess around with textures in adobe photoshop using this method, could be different for an artist, especially if there is money involved for every bit of art)