I've already heavily modified it to suit my needs, like mapping the fullscreen key to make apps fullscreen, menu for right-click (in QT, too), minus key for moving windows, etc.
Although you can feasibly still use GIMP in lxde, it isn't really useable. Because Matchbox crunches down windows to fit the screen, GIMP is pretty useable in hildon because minimal scrolling is needed (only with dialogs). But on the other hand, lxde respects the minimum height and width of windows, so the near constant moving of the windows makes it very hard to use. [because GIMP windows are huge].