It is trivial for a client or server to filter out files to be uploaded by type and size. That's why your unable to attach for example a PDF file to a post.
Discussion
I have mostly large-ish image files. So if I create a separate client they would just block/filter similar files after sone time?
They would route (relay) the files for you just not permenantly store them. They may temp store them but would delete to make room for newer posts. For large images, gigs, or videos I would recommend paying for a discord server and using them to deploy your files. Or run your own server and nostr relay.