I don't know if this is the right place to post this, but here it goes.

Does anyone have any tips or perhaps some visual tips on how can I make this following picture look more detailed, give it more of a 3d feel, give it more depth, but at the same time keeping it simple and keeping it 2d. Also I don't want it to look like the generic wooden background ones (talking about ball labyrinths).

The holes look OK, assuming the ball just gets stuck in them and doesn't fall out of view (they look shallow). The ball doesn't look spherical.

Yeah the ball looks like a floating disc - at least make the shadow a projection of a sphere.

Is that a cushion border, like on a pool / snooker table?  If so, it needs to cast longer shadows on the table from the top & left walls.  Maybe remove / lessen the opacity of the bottom / right wall shadows.

In 2D a lot of fake depth can be achieved just with light / shadows.  But the shadows must be consistent for the illusion to work.