artists_beware | looking for advice on reposting art (Reply)

I was leafing through a few pages, and I haven't seen a post directly addressing this, but if their is one, I must have missed it.

Only recently, I have decided to take on commissions for a a meager price and someone had taken an interest in it. I was completely estatic, and I've just now completed the art. However, this commissioner paid me with an e-check, which will clear in a day or so now (from the original commission date).

Originally, I found this to be a problem, but after communicating with them we agreed thatI would not hand over the art until I saw the money in my paypal. So things had cleared up there.

Now as I finished their commissions, I went ahead and sent them a note, telling them that the work has been done and I'll be posting when I see the money. I also made a request that they not repost my art to their gallery.

Some people are fine with commissioners reposting their art so long as they get credit and linkbacks, but I'm not really comfortable nor okay with that. And eventually I got a reply back saying that it's simply 'what they do, because they have no artistic skill of their own and they commission art FOR their gallery.'

The way they've replied make me feel like they're going to disregard what I've asked and they're going to do it anyway.
The thing is, I have the art, I'm waiting on payment because they chose to pay me in a format that I have previously stated that I do not accept. Am I in any position to make this sort of request? And should my commissioner respect that?

I currently don't have a TOS, as I've only started out taking commissions and I don't feel like making a huge deal out of it, seeing as I'm asking for $3 at most for my art. I have one in the works, but for smaller commissions I don't feel like its necessary.

In addition to this, I've also sold a character to this same commissioner for a higher amount as it came with additional art pieces. The payment for that character has yet to go through as well (they paid in another e-check), and we made the same agreement about handing over the character's art that we did for the commission.

I've commissioned a few pieces for this character from several different artists (mostly off-FA).
And I don't feel right in letting them repost several of these pieces to their gallery as well, but as I didn't draw the art for several of them (some of the drawings of this character ARE my own), do I still have a right to tell them no?

I have yet to reply to their last note, and I'm looking for advice on what to do before I reply. I don't feel that it's necessary to make their name public as this situation is still civil between us, but should things take a turn for the worse, I will.

edit: after explaining myself and talking it out with the commissioner, we have reached an acceptable compromise for the both of us. thanks for the advice, i'll be sure to mark this up as a lesson learned for the future.