I do design for open source projects, I've started helping out on the Gnome Project doing interface design.
• It's great for scratching an itch of 'I want to help other people'.
• It can be good promotion. The same way a good github account can help developers, stating and showing how you have participated on a open source project that is real is good for showing you can pull through on projects and deliver.
• It can be great fun to see something you designed being implemented and working. Even more fun if people praise you for your great solution to a problem. The thing with doing FOSS as a designer, you have to take alot of control - and push for developers to code your design. It's not just delivering a PSD, you have to work with the developers.
• If you solve a real problem, people will thank you.
Everything in your post is the absolute best case.
It can easily go the other way and your contributions can be ignored and never used, you will be reacted to with hostility by developers who think that design is an "extra" feature, and that even if you do succeed and something you do does hit a release, the overwhelming majority (nearly all) of people who use the software won't know you exist.
There are two sides to open-source development (at least, when it's not with people you know personally IRL) and one is, sad to say, generally not very pretty. Institutional hostility toward non-programmers still lives in a lot of open-source projects--usually the ones who need them the most!
(EDIT: Mind you, this isn't a reason to not at least try to contribute if you feel it's important to you, but the results are often not as rosy as your post suggests.)
You are aware absolutely everything you wrote is the same for developers too, even the programmer part;I've seen hostility towards people offering patches who are more users than programmers.
That's contributing to other people's projects period.
OSS is about scratching an itch, releasing code your business does but does not need to protect, or about self-gratification. While it can be a showpiece, you never get much in the way of fame out of it, no matter what you do.
• It's great for scratching an itch of 'I want to help other people'.
• It can be good promotion. The same way a good github account can help developers, stating and showing how you have participated on a open source project that is real is good for showing you can pull through on projects and deliver.
• It can be great fun to see something you designed being implemented and working. Even more fun if people praise you for your great solution to a problem. The thing with doing FOSS as a designer, you have to take alot of control - and push for developers to code your design. It's not just delivering a PSD, you have to work with the developers.
• If you solve a real problem, people will thank you.