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 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.)