Hey there, thanks for the feedback! I use iOS personally, so I try to ensure that the experience on there works well and is fluent :D
As MentalEdge mentioned, there is still on-going development on Thunder (not specific to the image viewer, but on other parts of the app). To help keep track of these suggestions, feel free to create new issues on GitHub. This will help us organize the feedback and be able to prioritize properly. If you’re not sure how to do that, let me know and I might be able to make them for you when I have the chance!