If you keep all the pieces in vector format, when you're done you can use the Pick tool to draw a selection completely around and enclosing entire drawing. Push one of the corner handles of the selection box toward the center to resize smaller. If you want to use raster tools to create some shading, you'll have better image quality if you re-size your vector drawing with Pick tool before converting to raster.
When done, export as optimized GIF or PNG.
Enjoy! Kate
