Why can't tiles inserted with "Insert Tile" be scaled like any other object?
Of course, it would be more ideal to be able to attach images to shapes to begin with.
@wolfscaptain Really, there is no shortage of potential features, so asking why some things are not possible is a bit annoying. It's all a matter of somebody figuring out how the UI should work and spending time on it to get it implemented. It could be you, too!
Issue relates to #396, though they are different approaches.
Resizing support was vastly improved with Tiled 0.12, released almost a year ago. This included making tile objects resizable.