Assets that are too large will have the “Publicly accessible” sharing option disabled. This means that you can only share the asset via private (email-based) sharing. We are working on new technology that will allow for unrestricted sharing, but for now we suggest keeping your assets under 600m triangles. Ideally, better to keep models under 200m triangles for faster load time.
There is no limit on texture or photo count, you can upload as much as you'd like for each.
To receive an email update when we allow for unrestricted sharing, create an account here on the help center and click "Follow" on this article.