Go to it folks - attach photos of your bikes for sale, your pet dog, whatever you want!
I should say there are some limits - 256KB per attachment, no more than 3 per message. You can also have attachments in Private Messages.
These limits may get reviewed as we go along depending on popularity; I don't have unlimited space on this server...
Another improvement brought to you by the hard working team here at Trials AUSTRALIA!
Cheers!