A few years ago I went to a Tamron sponsored Macro workshop taught by the late Don Gale. He was kind enough to give me a critique on my images that I've kept which might be useful to you too:
The only criticism would be the very shallow focus on some of the images....they were shot almost wide open.....and, with a macro lens, that's asking for trouble. Notice how, on the shots we did with the flash, almost everything is sharp....probably at f/11 or 16.