Character sprite sets can actually be any size the scripts will cut them into sheets. What $ does is allows you to treat a sheet as a single sprite rather than a set of them. From the help file: You can use PNG and JPG files.
PNG files with 32-bit color (alpha channel) are fully supported. Characters (Graphics/Characters) Files containing images of characters to display on the map screen. A character can be of any size, and a total of twelve patterns (four directions (down, left, right, up) × 3 patterns) are arranged in the designated order. In each file, arrange characters two down and four across, for a total of eight. The size of this character is calculated based on one-twelfth the width and one-eighth the height of this file. Adding an exclamation point (!) to the beginning of a file name cancels the application of the four-pixel offset, and also turns off the translucent effect applied by the bush attribute.Note that RPG Maker VX Ace displays characters offset four pixels from tiles so as to more naturally portray them with buildings. This is used mainly for object-type characters on maps, such as doors and treasure chests.
