I'm not really sure. One word prompts tend to give more flexibility, but at the same time it limits what people can ask for.
Regarding meta and/or other squee, I had an idea based on a community I saw somewhere else. It was fic-based, but used comment trees. The first person would comment with a character, the next person might offer a second character for a pairing, then a third comment held a prompt. But the tree format struck me as a possible way for people to share things they don't usually, so you could start with a character, add a thread for pairings/ships, another for meta, maybe another for songs/vids, and then one for fanworks? Comments starting each thread would need to be clearly labelled in the subject line for easier browsing, so maybe that is something that would require a little moderation, but if people are willing to participate (and 3wfdw is good for this), you could end up with something fairly impressive.
no subject
Regarding meta and/or other squee, I had an idea based on a community I saw somewhere else. It was fic-based, but used comment trees. The first person would comment with a character, the next person might offer a second character for a pairing, then a third comment held a prompt. But the tree format struck me as a possible way for people to share things they don't usually, so you could start with a character, add a thread for pairings/ships, another for meta, maybe another for songs/vids, and then one for fanworks? Comments starting each thread would need to be clearly labelled in the subject line for easier browsing, so maybe that is something that would require a little moderation, but if people are willing to participate (and 3wfdw is good for this), you could end up with something fairly impressive.