The challenge of including a Squirrel, Frog, Scorpion, Bird, 3 flowers, 2 mules and 3 scientists in the same illustration is that as much as I'd like to put them in context, ie - with trees, pond, rocks etc, I'd then have to take scale into consideration. That would add a whole other complicated dimension to an already rather subject-cluttered back-of-T-shirt design.
In attempt to unify everyone, I slid some rectangles into the background, and spent a few hours shuffling things around. Vertical rectangles, to reflect the forest in the background of the original Scientist/Mule photograph. At first, each animal sat at the top of its opaque, non-overlapping, equal-widthed rectangle. It seemed too... regimented. So, I reduced opacity of all the rectangles and stretched them out so they overlapped. But it looked rectangle-y. I sloppily carved off the edges.
The result is perhaps an unexpected combination of organic brush and ink drawing with a graphic background. It might need some more tweaking. But it's interesting at the very least, and consider also all the other Science Research themed t-shirts you've ever seen in your life. Usually it's a boring logo, or a re-purposed scientific illustration. This has got much more personality.