electro_ball.png needed to preserve one whitespace tile which tools/gfx would normally remove. Preserving a list of tile indexes has been added as a general feature to tools/gfx.
sgb_border.bin needed to remove the 20x18 center area of $00 bytes. This is achievable with the standard tr utility.
For images composed of 8x16 sprites.
The width has to be manually passed in. If this were an rgbgfx feature this would not be necessary.
Fixes 647f9b4452