I sure do have āspecific forward looking, positive suggestionsā, though what follows only applies to the wallpaper side of things.
- Return to using the āWallpaper contestā naming
Itās succinct, to the point, and parseable at a glance. It instantly tells whoever comes across it that āthis is a participatory thingā. Itās will also be familiar to those whoāve been using Ubuntu for a long time. I do get e-mails asking why Ubuntu doesnāt have a wallpaper contest any moreā¦
- Promote the wallpaper contest outside of the Ubuntu member channels
Pinning a topic in /r/ubuntu is useful, but go bigger and promote the contest beyond the orange bubble.
Let Linux blogs know the contest is on, when it launches, what the deadline is, but also reach out to photography blogs and groups on Google+. Get them to share the details with their members; get Ubuntu to promote it on their social media channels for greater reach.
The aim should be to promote the contest to a diverse and varied set of people, not just existing Ubuntu contributors.
And, above all else, continue to bang the drum during the contest. Many potential entrants will forget about it after the initial hype so do keep reminding them (e.g., ā1 week leftā, āfinal 24 hoursā. etc 
- Rewrite the rules/criteria
The longer the list of bullets points, the more of a hassle it seems. The criteria has been recycled and added to since Iain was in charge. Iād condense it down into āthree core rulesā or something ā and donāt, on a wiki page, tell people to āfind more informationā on the wiki without linking to said wiki page. Group/merge some of the points together (e.g., resolution and file size; license and ownership, etc) to make the rules more digestible.
One thing iāve always noticed: the wiki and photo pools often omit the deadline. Thatās an important bit of information people will want to know.
- Be open and transparent about the selection process.
Jane SIlber and Barton George helped to select the most recent set (!) which wasnāt known until after. Itās motivating to know who your snaps will be appealing to (especially if those people are notable/well known) are involved. It humanises the contest.
- Utilise designers and their expertise
Related to the above point, but itād be nice if designers/people with expertise in creative subjects were involved. Ubuntu still has designers. Perhaps ask if any would like to be involved in the selection process? Like ānamedā people it lends a level of seriousness.
A big participatory contest needs a big celebratory climax. A bit of public exposure for the winning artists will help them feel it was worth their time getting involved, while those who donāt take part will be still be interested to know the outcome too (and seeing people get a public thanks will make them more likely to take part next time).
Limiting the number submissions each user makes is still a good idea as it forces people to assess their own work.
The idea mentioned above about introducing categories sounds like a great suggestion. It would broaden the subject matter and, with categories like ātechnologyā and āspaceā broaden the appeal to entrants who might otherwise thing their subject matter wouldnāt suit.