Yeah, mouse paintring is cool and all, its a bit like painting with a big brush i guess, rubbish for smooth lines without lazy lines script but its possible to make nice paintings with mouse i think. craig mullins did for a long time.
but the wrong hand? why bother?
ok the thing about graphic designers is theyre more into doing websites and printed stuff, so they learn about type, printing, layout, stock image libraries, photoshop, illustrator, indesign, things like that. very little drawing really. so think about what you want to do and figure out who needs stuff like that and will pay you to do it.
for the image, get reference and study it. have you ever seen one of those red and white toadstools? theyre call amanita i think, the ones gnomes sit on. you can dry them and boil them up and get really high off them buit thats another story. point is in a forrest at night theyre not going to be bright red. think about how the lighting will affect your objects.
if you want to go more figurative and illustrate-y, get reference for that too.