Generally, any content posted/uploaded to a public form becomes the property of the forum although I note that the terms/conditions of this site don't discuss the subject, but generally once uploaded rights are permitted for the forum owners to do with that content whatever they please.
Other users 'using' that posted content is cheeky but unless you explicitly state that the content is provided without a public reuse license, you're essentially inviting others to use it.
However, I would say that in the instance of your CU pictures, they're using the imagery fraudulently as they're passing it off as their own work, that's more the issue in a greater respect than them merely reusing your photo.
A tip here for you guys - if you're ever concerned about the reuse of one of your photos, go here:
http://www.google.co.uk/imghp
Drag and drop your image towards the search box and a dynamic area will appear instructing you to drop your photo there - Google will then crawl it's index and find any direct match for your photo, listing the websites on which your imagery is featured.
Using this method, I found that your photo has actually been extensively reused on other websites, companies you might wish to call on Monday
Personally, I'd put together a nice 'legal' looking letter requesting compensation for fraudulent use of imagery, make it look official and you may get a few cheques in the post
http://www.renevation.com/page4.php
http://www.sbelectrical.biz/gallary.html
http://pedelectrical.co.uk/
http://www.hotfrog.co.uk/Companies/South-East-Electricians/Consumer-Unit-Fuse-Board-Upgrade-160722
http://www.4siteonline.co.uk/
http://www.mphservicesuk.co.uk/home/picture-gallery
http://www.dmacgregorelectricalcontractor.co.uk/services.php
http://west-electrics.co.uk/services/
I hope that this helps.
Cheers,
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