Just one image file can take up as much space on the message board's file server as hundreds or thousands of simple text posts. For this reason, it is common for board owners to limit the number and/or size of attachments which can be directly uploaded to the board's servers.
The way around this is to use an image hosting site as a go-between. Some popular ones are imageshack.com, photobucket.com, and my favorite, http://www.postimage.org.
You can upload image files to postimage.org without creating an account, with no advertising or pop-ups. After uploading, select the Copy to Clipboard for Thumbnail for Forums (1). Next, simply paste the link into your forum post.
My hobby is finding things. Having found most of my own, I am happy to help others find theirs. PM me!