Searching images directly in Miro and adding them to board with one click is a great feature and I use that a alot. But most of the time, for every single thing, I have to add too many images first and then I have to look at what they really are on the board. Thumbnails are too small and I add at least 10 images then delete 9, and to do that I have to wait them to load, then move them because they are loaded on top of each others and finally choose one and delete the others. This is just a huge time waste for me and unnecessary data flow for your servers.
As a solution,
1 - If you could add a slider for thumnails size, or
2 - Like Google Image Search on web browser, when I click on an image, there may be a dropdown area with bigger size image view, or
3 - Mouse hover on image can show bigger size, like imagus chrome extension. (but this one is a problem when someone uses with touchscreen)