Goto FSF. Open up Calculator, choose scientific mode and choose Hex. Type "2D0" and click dec. That number you put into FSF where "needed bytes are". Click search beginning of rom. Than turn that 16 number into 1. Hit search. That offset will be used in UNLZ. Write to rom, check the pointers box, and insert the new offset into the image area. Click ok and it should work.
I never tested this with a Pokemon before, but I did it with the into sprite of the hero. I don't see how it'd be any different.
And by the way, when it auto aborts...DO NOT CLICK OK, click CANCEL.
Hey I also have this problem, did you find out how to fix it
What will you have to consider here is that your sprite has about 28 colors in it.
You decrease the color depth to 16 colors, when you insert the sprite UNLZ gba you dont get any error.
BUT THIS WILL NOT WORK BECAUSE YOU HAVE YOUR IMAGE IN PNG FORMAT...
The png format will not provide a transparent background and ruin your ROM