Well, make sure they're not too obnoxiously big, as that does get annoying if all the pictures take over half of the page.
Other than that, making them look the same is good. Don't switch between cartoon, real, and whatever else style for the pictures. However, this might just be my own nitpicking, and we all know how nitpicky I am. xD
And this really does not belong in Advanced Editor Forum as it doesn't involve the advanced editor in any way.
I would say this belongs in Writing Workshop.
@Killa_Robot @Endmaster @Whateverothermodwantstodealwiththis