After reading these posts:
I was wondering, how to present the most appealing competition themes to our community.
I'd like to suggest to create a common Meta page (wiki style), where new themes can be posted and voted on. Each theme would be an answer you can vote on, community edits could help to enhance themes requirements.
Such an approach would surely be more visible than a chat post and would leave a nicely structured and comprehensive selection list to vote on. I also think it is a better approach for users which are not used to chat.
This Meta Page could be made HOT or Featured and placed on the right sidebar once a month during some days/a week. Highest vote wins. Once Voting is over, the winning theme is removed and all other themes remain, but are reset to 0, voting starts again.