Thats's pretty much what I mean, MFME & JPeMu only have rectangular graphical lamps. If we could cut out the lamps manually it would avoid masking unwanted areas altogether. See attatched pics...
Could you not implement png support? You'd get an alpha channel instead of the pink area, so when loaded into your editor you only see the visible part of the image that you need (so no more masking).
Further to this, you let the users continue using programs like photoshop/G.I.M.P for the majority of the designing work so should only need to offer simple placement tools for your editor.
You can also perform simple alpha blending between lamp sprite and covering image, so one sprite acting as a lamp will conrtibute brightness to any sprites covering it (as it should).
bitmask