I have a couple of Heero and Relena sketches that I'd like to submit, but I can't add them to the gallery. I've even tried the "add to a group" button on my deviations, but there was a message saying that I couldn't contribute to the group.
Go to the deviation page and click the add to a group button. There, you'll see two tabs. Select the "suggest" tab. Anytime you want to submit something to the group you can use these steps.