I am making png images that have transparent backgrounds. Right now I am working on things from the ocean like fish, etc. Here is a demo: http://photostockrus.com/?ims_gallery=ocean-items-png-transparent I have a package of 30 images so far that I would sell for $10. They would be for your personal use only. I have images in almost any topic. If you have a need send me your want list and I will make you up a batch. I also can do other image editing for you. The image below was added using their system. The originals are much better.
No offense, but the images in your "demo" are poorly cut out. Rendering images isn't that difficult, especially at that level. Should practice more on making cleaner cuts and no remaining white/colour around the edges. They're not worth that price, even. Anyways, good luck.