The Imagemaps plugin allows you to place any image into the game. To use it:
Submit your image for approval in the #smp-imagemaps channel (we respond quickly).
Once approved, use the /imagemaps place command on the server:
/imagemap place <filename> [frameInvisible] [frameFixed] [frameGlowing] [size]
For example:
/imagemaps place bedrock false true true 4x3
will create an image named "bedrock", where the item frame IS NOT invisible, the frame IS fixed, the frame IS glowing, and has a size of 4 blocks wide by 3 blocks tall.
[frameInvisible] and [frameFixed] can be modified after placement. Right click the item frame using a wooden hoe to toggle [frameInvisible], and shift+right click to toggle [frameFixed].
The resolution of a 1x1 map is 128x128 pixels. To ensure images appear high quality, scale them to multiples of 128 before submission (e.g., 4x3 is 512x384 pixels).