The suggested method of using specific image IDs (like those from
Open your image editor and set the canvas size to 24x24 pixels.
While most official sources state 24x24 pixels, some community sources and private servers use a 32x32 size, so double-check your server's rules if you're not on an official server. Also, the hot pink color (Red: 255, Green: 0, Blue: 255) will be rendered fully transparent in-game for both .bmp and .gif formats.