A little fix to make file system paths cross platform. Hard coding them as "/images/" or whatever won't work for systems that don't use the forward slashes (ie. Windows) so I've used os.path.join instead.
Also I went ahead and moved the pygame.image.load calls out of the game loop and into Gamescreen.__init__. The game seems to be much more responsive now.
Make filesystem paths cross platform.
Move all image.load calls into Gamescreen.__init__
so that graphics aren't reloaded every time they are used.