On the old forums, I think this was possible...? Either way, any plans for this in future? :)
Forum/blog post attachments? It's planned for the near future. Like many things there's backend support for it already, with the frontend integration still needing to be written :)
There's two sets of quotas, the member quota and the project quota.
If a member adds an attachment on any forum, it'll be counted against their personal quota.
If a project owner adds an attachment on one of their projects, it'll be counted against the project quota. If they do so on another project it's again counted against their personal quota.
The personal quotas aren't very large at the moment, but should accommodate a few screenshots just the same. It's just that there's more members than projects, so we can't go nuts with attachment quotas until we either move to a bigger server, or we offload some file hosting to a CDN, or both.
We'll be making that call based on the technical merits mostly. There is a financial consideration to be made as well in choosing between a bigger server and a CDN. Between the two we'll come up with an answer on how to proceed soon enough, but until then the file storage quotas will be a bit on the conservative side.