I have drawn small gfx in dpaint many times. I have to do that for making game gfx.
What I do:
1. Decide how big my gfx is allowed to be.
2. Draw 2 lines in the upperleft of the screen at 1 pixel beyond my gfx max size. So I know I have to stay inside this "box". 2 lines like this: _|
3. I draw my gfx into the upper left of the screen inside the "box". I use the rest of the screen to cut and paste other gfx or to do experiments and things.
4. When I am done I pick up my gfx as a brush. Then save the brush to disk.