Are all templates accepted?

No. We have a high bar for our templates and each goes through at least one round of full code review with the MUI team and sometimes multiple rounds. We're aiming to do this as efficiently as possible but the end user's experience and having a quality of templates in the marketplace are of primary importance. At a high level we're looking for:

1. Clean, well-considered design
2. Organized, high-quality code that mimics MUI Core library style
3. Targeted purpose, meaning templates that aim to solve a specific category of problem
4. Are different than other existing templates on our marketplace
5. Creators that have shown a history of excellent customer support

We've got a longer, more technical document outlining the whole process for review in the following article so take a look at it when you've decided you can hit the points above and follow the directions to submit your template.