Can't wait to see what you come up with! I'm scrapping older boys these days (9 and 11), so I want boy kits that are less cutesy and more tween-appropriate. Non-themed boy kits are always good, but if you prefer to work with a theme I'd use sports, brothers (getting along or doing things together), hanging out (at home or with friends), creating (Legos, drawing, etc.), exploring outside, reading, gaming, something for scrapping their view of the world (thoughts/opinions on anything from politics to friendship to favorite books), being silly, and tween attitude.
There's no specific thing I need to see, but a lot of non-floral elements are a must. My oldest hates it when I use anything he'd consider girly on his pages. I still like to have foliage, but not flowers.
My preference in colors is lots of them! Girl kits often seem to have a much larger palette than boy kits. Or maybe it's just that boy kits have more shades of the same color (ie, 3 blues) and more neutrals.