I agree with Mystical, Joe and the others, you really have to concentrate on yourself. By putting all your energy on mastering your skills and building a good reputation, you will see a return... it will serve you better than worrying about the hacks... worrying about hacks could be a full time job by itself. We all deal with them. Just do better work that's reasonably priced.
Quite a few of us have had our work pinched and used on other sign makers sites... I'm sure shops would appreciate a heads up. I have had sites and Facebook pages removed when the shop did not comply with my DMCA request. Many shops do this by the way, we have had a few here... they say they are not marketing these signs as their portfolio but for "inspiration" The 2 latest shops to try this ploy are out of business.
What kind of jobs do you dream of doing?
I went to your site and the offending site. I can clearly see work they didn't do - not cool... but I also saw work with copyright you clearly do not own on your page too. As minor of an infraction as it may seem, it's still the same thing. If I may ask, you say you have been doing this for 2 years... what other training or experience do you have in graphic and signage. From what I have seen, you need to develop an eye for design, your work is "typical" sign work of someone with little experience and no formal training. I ask this of newbies all the time... "how can a business trust your expertise if you have no experience"... well I usually get "you have to start somewhere" and it's a fair response. But is the work you are now doing going to get you to the dream work you want to do? I'm thinking this guy is getting it because of his unscrupulous tactics... well, it will come back to bite him in the arse... he's not impressive at all so it's not going to be hard to be better than this guy.
Just because people purchase your services and signs does not mean you (or your competition) are any good.
If I were you... make you're website impressive... your Facebook should have only the best work... it does not to have to be award winning, but the bad work you have on there reflects on you... your business... and your brand. If there is work you want to do, design it and add it to your portfolio and say that it's a concept design. If you have no formal training, get busy learning it... there are plenty of books and tradeshows, ask here, show your work and ask for advice.
I highly suggest the books:
Sign Craft Magazine....
Building a Small Business Brand: How to Turn Your Brand into Your Most Valuable Asset - Dan Antonelli
Mastering Layout: The Eye of Art Appeal - Mike Stevens
Now I may catch flack for this recommendation because the guy was on this site and totally lost his chips - but I think you would get a lot out of learning presentation - it's not the best writing and has a lot of inaccuracies but well worth the read.
Inside Sign Design - signdesignbooks.com
I just finished a book... mostly about traditional graphic design, but still inspiring...
House: The Process is the Inspiration: House Industries
Another favorite and I dig his videos:
Draplin Design Co. Pretty Much Everything - Aaron James Draplin