You can either become a supporting member by contributing $25/year to wranglerforum.com, or, if you can't spare that, you just have to upload images to an image host and link directly from there. That way, you aren't using any storage space on the forum's servers. You're using storage space elsewhere.
Here's a tutorial
on how to upload images to Photobucket using your iPhone, and how to post those images here on the forum... all from your iPhone. It's easy to do once you've gone through the steps one time.