Should Images Be Stored in a Git Repository?

Your plan sounds great! I think you are off to a really good start.

My only advice is in regard to you Developer Workflow. I think you're dev branch may become problematic, because developers will be merging code willy-nilly then they think its ready.

If both branchA and branchB, C, and D are merged into dev, and it fails, you can't be certain which parts are necessarily failing. Also, if someone pushes up something with a conflict, you dont know who it was. Madness and insanity are bound to ensue.

If a feature turns out not to be ready, and code needs to be backed out of dev, other developers will have already pulled down their additions. Those developers then will merge back into dev, unwittingly re-introducing the broken code. Madness and insanity are bound to ensue.

You're going to need a couple steps of separation to keep untested code away from tested code.

This all depends on the skill sets of your team, and how you actually work together. What follows is my solution to problems of a quickly expanding team with differing levels of git knowledge and different levels of developers code dependability.

I always try to tell people to not simply think about developer workflow, but testing procedure, and release process. They all need to be planned as part of a singular process.

1. Lead Dev or Release Mngr (whoever) creates a new release branch based off master. This branch will be a container for anything going on it in the next release.
2. Lead/ReleaseMngr creates integration branch based off release.
3. Developer creates new feature branch (or topic branch, whatever you want to call it), based off the current release branch.
4. Developer tests locally, is happy.
5. The developers feature branch deployed somewhere and tested by QA independently of any untested code.
6. QA signs off on feature - it gets merged into an integration branch. (ideally, IMHO, only after the feature branch has been rebased off release, to force the conflict resolutions )
7. QA tests the integration branch which is just the release branch + this one feature.
8. QA signs off - integration is merged into release (if not signed off, integration is blown away and recreated based on release). This is the reason for integration. No one pulls form this branch, and it can be blown away as needed.
9. Now the feature is in release, and can be shared with other developers making features based off release branch.
10. Release is good, merge to master. Deploy, make a new release branch based off master.

I know it sounds like a lot, but it really will save you from the headaches and, in my experience, are inevitable with large projects with logs of people having differing levels of knowledge.

If you have a small team with a simple release process, or a team that is very experienced - all this may not be necessary - but do be aware of the inherent problem with testing multiple people's code at the same time in your dev branch.

All that said, its my understanding the GitHub team just lets everyone merge into master directly (after a brief code review) and auto deploys ~30 times a day.

The repository format only changes very rarely, and it never changes in a way that is backwards-incompatible. IIRC, the last incompatible changes in repository format were back during the original 12-day period when Linus wrote Git, i.e. even before he published the code.

I think there was one backwards-incompatible change in one of the remote protocols many many years ago. However, in that case, the server will tell you that you have to upgrade your client and even which minimum version to upgrade to.

Of course, if you go far enough back you will arrive at a version that doesn't even know the current HTTP protocol at all.

But in all of the above cases, we are talking about clients that are several years out of date.