I'm talking about designing your own tileset from scratch.
In my game, collision detection will be done with tiles, 2 types of downward slopes (i.e. shallow and steep slopes), and 2 types of ceiling slopes (in areas with ceilings). I'm going for a more 'top-down' view akin to something between Donkey Kong Country and Megaman X (both collision and view-wise), but I can do more free-form collision-wise if it's easier to design/draw for.
Modularity in visual assets is my main desire, but combined with enough variation in centerpieces/variety/details to keep the visual interest as strong as possible throughout a particularly long and continuous level design with no screen-breaks. I'm aiming for a look between a 2d fighter and platformer -- i.e. enough visual interest like you'd have in a nice fighter-level, but not so much detail that it can't be reused in other parts of a larger platformer-style level. The problem with the platformer level is that it ends up looking somewhat too repetitive if I repeat large detailed visual assets too much, but I want to keep the wow moments too, although I don't want to draw too many unique graphics.
I was thinking that maybe tiles can allow some of the more unique formations in the level by redrawing only a small portion of the larger tile, but I was also thinking that perhaps drawing many larger tiles with large variations might also work better? Which approach do you feel is generally better and/or faster in your opinion?