You can load images into the gallery with no limits and then link to them in your posts but as you have pointed out the ability to upload directly to threads is somewhat restricted. Hopefully the gallery option will be a suitable option.
Gallery images are editable indefinitely and you cane move them around to various folders and categories as you wish and the link in your post will remain valid.
The other side benefit is that gallery images display in the rotating picture lottery at the top of the portal page