My biggest problem with roll20 to date is how often I accidentally move images on my background layer. If I want to add a fence over my grass texture, I feel I should be able to do that with worrying about my mouse being on the correct pixel. If I add a door to my dungeon with the intention of turning it so that it will look open when my players approach, I'd like to be able to do so without worrying about moving the entire dungeon. This is a constant problem, however. I'm aware of many work-arounds, such as working on the object layer and then switching the assets over to the map layer, but this is far from efficient. A simple right-click>lock asset option seems like the most straightforward solution. It would also serve as an efficient way to temporarily lock a player's token without having to change token ownership. I think the ability to lock any asset in place on the map would be extremely helpful, all around.