I can't provide screenshots because RoughTrade's website actually blocks that, and most of the forum is hidden from non-members. But I going to try to describe it better. (anyone can sign up if you wanted to check it out. https://www.roughtrade.org/the-workshop/forum
At Rough Trade there are three different kinds of picture prompts, one is Monday drabbles (though they use drabbles to mean 1000 words not 100 words), the second is Thursday vignettes (1000-2000), and the last was Sunday prompts (no rules). There was also word, first sentence/one sentence, and characters. The prompts weren't super important, it's more about the process. A prompt is posted and there is no deadline, it's mostly for inspiration. So, there is no stress, anyone can do the prompt at any time, and it's to help inspire.
This is one I did for novachaos
& this is a screenshots of the post 1
I hope that helps :)
Also, maybe these prompts could be where anyone could post a prompt?