Liam,
You should be able to attach images to your posts, though there is a file size limit to this, if you keep it under 200kb you should be OK.
Or you could use your free gallery space, and link to the image there?
Again, the smaller you make the files, the better performance will be, and also the less chance there is of the server software that creates the thumbnails, throwing a wobbly there will be too.
Other than that you can try imageshack or photobucket?