N.B. – this post was written when the old website was still in use
Photos, diagrams etc. can be included in forum posts, but only by inserting into your post a URL (web address) for an image that has already been uploaded onto the web. Ideally we would be able to upload to the UKWA website’s Media Library, but there is currently no way for users to do this 🙁 [N.B. This is no longer the case – most can now upload in this way.]
If you have your own webspace, or a blog or something similar (perhaps Facebook?) you can upload images to that. Then, when composing your forum post, use the “Insert/edit image” button to insert a link to your image.
A box will appear on the screen and you need to paste the URL (of the place where your image is stored) as the “Source”.
The main column (where you’re seeing this text) seems to be 456 pixels wide, so if you make your image this width (or slightly less?) it should display correctly. [Considerably wider now, ~835 pixels, at least on desktop & laptop devices.]
(I haven’t worked out the subtleties of the dimension controls and how they interact with the site.)
Edit – The new website has a different page layout.