Finally fixed some fairly big bugs with the water and dynamite bricks and have uploaded a video of the level editor/tester in action. Ignore the low framerate, as the screen capture software is to blame.
@ Glasskatten, by rendering in realtime do you mean the bricks blending together in realtime or the ability to easily switch to gameplay mode?
For bricks blending I have a loop that makes new bricks check around them for surrounding bricks of the same type, and based on their surroundings they change direction (each direction has a different image to match the surrounding bricks). The gameplay switch is as simple a using the real gameplay objects in the editor rather than placeholders. The editor and game are on the same frame with their code in seperate groups that can be switched between.