I just spent a couple of interesting hours researching this painting on TinEye [reverse image search engine], since I saw it on a FaceBook Dragons appreciation page and wanted to leave an attribution there. As I've seen mentioned earlier in this string of comments, your picture has been posted without attribution in a LOT of places, some of which are taking credit for creating it and/or selling products using it as a logo. I just do this sort of thing as a hobby [and Dragon art enthusiast], but I recommend that you Google Search 'TinEye' and download their free browser add-on, which makes it easier to search for copies of your art online - or of course you can use the Google reverse image search for images, which is accomplished simply by clicking on the camera image in Google Search and uploading a copy of the image you want to search for. The results are similar; but each one finds results the other one misses.
Good luck with your art, and I'll make sure that Dragon's Cavern on FaceBook gets your attribution.
Oh, and thanks so much for the beautiful Dragons and other fantasy artwork!