Currently (Tropy 1.0.4) I'm unable to add vector images. Most of my scientific figures (sketches, plots, drawings) are SVG, EPS or PDF files. It would be great to be able to work with those formats too.
P. S. I've also been thinking that it might be interesting to add support for TikZ code snippets, rendering them to preview on-the-fly. This might be very useful for LaTeX users.