I suppose then, one solution is to have the image or object to be representative or a metaphor of what a quote means.

For example, let’s say you use this quotation: “If you don’t take steps forwards towards your goals then you’ll always be in the same place despite having any.”

Well, that could be represented in a lot of subtle ways. One example is to put two square framed photographs up next to each other about 10 feet apart, one frame is a pair of fancy shoes in profile pointers towards the right, on a white background like a stock photo, and have the second frame be a chef’s hat (to represent career change goals to be a chef) 10 feet to the right. The space between the photographs represents the journey. “If you don’t take those steps (the fancy shoes) then you’ll never close the gap (and be closer) to your goals.”

It’s totally inconspicuous. It’s not a very creative example or an arguably minimal one but it fits your request for alternative motivational decor. So choose a quote you like and find ways to interpret and define it through objects or images. The interpretation you choose will also be meaningful to you because you are the one who expressed it that way. A different person will take the same quote and define it their own way.

As far as things to bring anxiety down and mood up without much thinking, I think you’d have to rely on things proven to boost mood and lessen worries. For example, the look and sound of moving water has proven to be psychologically calming. Can you add a miniature office fountain that you can plug in somewhere where the cable can be hidden?

Live plants do the same thing, the color green is associated with life, and lifts mood and provides “positive distractions.” If you’re engaged with nature then you ruminate less, is the principle.

As far as more science, there is study on how patients in a hospital recover faster if they are allowed a window view into green scenery such as a hospital garden, more so if they can walk in one while in recovery. If a patient was in a sterile environment such as yours, they tend to recover slower than patients with a view or access to nature via a park or garden.

Good luck!