I see you wrote that you’re thinking about making it FOSS. What’s the alternative? Paid software/non-free license + Open Source or proprietary? If you’re low on time and don’t have the capacity to maintain (bugfixes/reports from users) yourself then I say proprietary is a no-go. Then about the license - IMO (though I don’t have hard data on that on hand) people much more likely contribute to FOSS as opposed to locked in license + open source model.

As both user and developer - user CAN contribute but the developer/maintainer SHOULD add the screenshots.