Modifying or "developing" a specific piece like the "long piece" (I-piece) in a Tetris ROM for MAME generally requires or using cheat codes , as the game's logic is hardcoded into the original binary.
: Change the instruction so it always returns the ID for the long piece (often 00 or 01 depending on the version). Tetris Rom Mame
: Use a tool like Tile Layer Pro to open the ROM and find the graphics (sprites) for the I-piece. You can redraw it, though its "hitbox" is defined by the code, not the art. Modifying or "developing" a specific piece like the