Displaying easy to understand patterns on 2 sides is a little bit more tricky, because obviously there is now less choice in laying out stickers, as the facelet 'store' real estate has been reduced from 5 to 4 faces, or even less. But it is still possible to design attractive textures though, even for higher order cubes.
Let me give 3 examples:
The first one is a 4x4x4 animated (real time) Analog Clock Cube
, for which both sides F and R have been used for displaying time: hours/minutes on face F and seconds on face R.
The second one is the Astro Cube
on which comet Halley can visit any of the 6 planets, where all 6 faces have been used.
The third one is the Maze Cube
for which it has been demonstrated that 156 single-loop solutions passing by all 6 faces do exist.
As you can see, there is no unique solution or general design procedure. All textures have to be designed using a case by case approach, usually by trying out a number of solutions. Some tricks to build 'good' textures do exist, although not yet published.
And finally, even if an appropriate texture has been found, then remains the task of checking it against legal cube states by using a list of specific algorithms.
But maybe the design you already have in mind could be simple enough and could be developed in a more straightforward way...