Thought I would throw in an answer to this because it's actually a great question in general.
Personally I think this sort of interaction can be a lot of fun, and making a set/finding pictures while in some sort of sexy predicament can be a lot of fun (or even with some very basic rules for the pictures themselves). However, there are some things that are worth thinking about.
For one, making a set while also doing other things is slower for sure if I'm using quite a bit of text or having to plan the set out first. Just gathering pictures doesn't have this issue. Having to 'fetch' mid set can break the momentum especially if there is any need to clean up or sit at a desk where I can actually do the fetch part comfortably. I'm pretty picky with finding pictures though, so that probably contributes to the momentum break for me. If the fetch happens at a natural break in the set (or at the end), again this is no problem.
In terms of feeling like you might be forcing anyone to make certain things, as long as everyone is having fun it shouldn't be an issue! But I can think of a couple ways to make it feel more fair. One is just require them to make their next set at least X pictures while following the fetch task, so it's not limited to specific thing they're making. Another is to make it an optional trade or challenge - do the fetch task and in return get a reward.




































































































































































































































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