Position is everything in this case. Pics?

It would help to know the USDA zone, the bed's sun exposure, and particularly the bed's location/context. Design principles may be abstract, but an actual garden isn't.

The landscape is bigger than the rectangle in which you will place the plants. Everything around that space affects that space and that space affects everything around it. You can choose to ignore that reality while designing, but it is real and will affect anyone observing that landscape (some more profoundly than others)

The dilemma is caused by your subconscious being aware of that bigger landscape while your conscious reasoning is ignoring it. Pay attention to more of what is around the rectangle and it will become much easier to come up with a suitable composition.

If you already have walks all the way around it I'm going to assume a formal garden might be the way to go. Something with a center water feature that is tall like a fountain, and then plan out from that feature. Possible a couple of topiary evergreens for 4 season interest, a rose groundcover for a long bloom season of color and then special plants that you really like placed randomly in the bed.