Change appearance of hot spot question selector marker

The workaround I've been playing with is to use a Pick One or Pick Many interaction.  I cover the entire area with transparent rectangles and then customize the "selected" state of each with the icon I want to show when the learner makes their choice.  Then I make each of the transparent rectangles an answer choice in form view, and indicate which is the correct answer. 

For example, I needed students to find three cats hidden in a picture.  I covered the picture with a grid of 40ish transparent rectangles.  For the selected state of each rectangle I added a cat paw icon.  I changed the size of some rectangles  to fit the cats and other likely options that students might choose and adjusted the placement of the paw on a few as well, but for the most part it was just an exercise in copy and pasting.   The longest part was setting all 40 rectangles as answer choices, but once that was done, I had a pretty effective hot spot alternative.  Students could select any place on the picture and a paw print "stamp" would show.   Once they were satisfied with their choices, they could hit submit to see if they were right.  

It worked well for an interaction where the selection areas were pretty large, but it might be a more challenging strategy if the items you want learners to select are small (so you'd need more rectangles) or if the borders are weird (like a map hotspot).   Hope this helps.  Love to hear other strategies or even ways to make something like this more streamlined.