I really relate to that - even though I'm a writer I'm very shy of joining in and I hate to share work early on because it's usually rubbish. But that's not something the challenge itself can change - it's up to us as participants to make sure we're as welcoming as we can be and to try and think about what it's like for other participants.

Like I said elsewhere here, perhaps a friending post for artists at an appropriate point in the timescale might be helpful?