I have advised people to use cheap logo services as a way of getting a decent first draft--something they can use temporarily or take to a more involved designer for improvement.

If I pay for a logo (cheap, sure--but also with no opportunity for feedback) I expect to get (1) ownership, not a license and (2) the source files so some other designer I hire can improve it (or make it suck worse, or just make it black and white--doesn't matter, it's my logo).

Re: ownership, if you want to require me to agree to let you display it in your gallery, that's reasonable. (Even then, if you get pushback, consider an option to buy my way out of that. If someone's that concerned, just take their money and put the next one in the gallery.)