There are a couple marker projects in the Getting Sketchy series. I know Matt did a lime slice on green paper really came out amazing, the biplane done just a couple months ago was another opportunity for markers, and if combining with colored pencils, most any subject could be completed quicker with markers combined with colored pencils. I really like multimedia projects, though. Ink and wash, gouache/watercolor and colored pencil, and several other mixes that allow me to cover the large areas quickly then go in and add more detail later. There was also the cafe in the most recent season of Getting Sketchy which was done with only about 4-6 (sort of clashing) colors of markers and started out looking like a disaster then ended up coming together great.
There’s another thread here where a member is drawing Dr Seuss style fun house portraits you might like as well.
Just about anything can be done when combining colored pencils and markers, from simple to quite intricate and vibrant objects like the South American parrots and other birds that cover the whole spectrum with their coloring. Some take them as abstract concepts, some are photorealistic, try a few out and see what happens.
I tend to pick subjects that I like to start with, but not like so much I’ll be bummed out if it turns out crummy. I’d always start with graphite rough layout/sketch no matter the medium, gives me an idea if it will fit and I can get proportions right (biggest difficulty, next to rushing through all of them).
–ETA: Somehow forgot this recent one I enjoyed doing with non-standard markers: Gettin Sketchy - Pineapple with markers - #10 by ThatOtherGuy