I don't exactly have alot of photo editing experience, I DID take a digital photography class a million years ago, but mostly forgot EVERYTHING. I don't even have photoshop on my computer anymore, so I've been using pixlr.com to play around. I discovered that in about 10 min I could make my own specimen print (roughly the same amt of time it took to troll Etsy looking for the perfect vintage one that happens to be way out of my price range)
basically you just go to pixlr.com, choose pixlr editor advanced, create a new image, for poster size choose a width/height of 1800x2700 or larger, google image search for sweet clip art of what ever specimen you're looking for, save the image then open it in pixlr and cut paste, cut paste, cut paste...you get the idea.
This is as far as I've gotten, but the next step is take it into kinkos and print it up!