My Other Journal Has A Nightwing Icon. Go you, ideal for silhoutte. If you want concrit, I think the midsection and the stretched forward arm needs to be different to show the muscular tension necessary for that jump in the black on white as well (but I wouldn't know how ATM).
The wooden ball is actually ok, I think it only needs the top ring fixed and a firm crisp outline (that I do know, how pencil tends to look worse than it is).
And while I'm at it, I printed out the figures (printer nearly died) and was thinking of which technical objects to draw, but then I failed at deciding if I should take something I really know/in flat or something I then google.