nah
you just need a ref of your oc, like REFFFSS, if you're not prepared
so say you have a oc but they're not too complete, you'll add visual refs to your stash so they'll know what to look at, say you put clothing in your stash that you think your oc will wear, they will just look through that and draw your character in their outfit wardrobe orz
or more refs for like hair and stuff but just be descriptive