Are the cabinets white or grey? Looks like white?

I would pick a color and a unifying item and display like in this picture;) click to enlarge

Plymouth Kitchen Renovation · More Info

Placing similar objects in each of the top cabinets looks clean and uncluttered. For example, vases of all the same color (you can vary shape or size or keep same), varied artificial green plants in the same container. To avoid a disorganized look, you need to pick a theme and carry it through each cabinet.

I would do a bunch of pottery/dishware in the same color scheme. Martha Stewart is really good at this look. I was going to suggest all white dishes and such but since the cabinets are already white, you probably want some contrast.

I agree with previous poster about removing the middle shelves if you can get items with enough height. I wouldn't do any greenery because when it's enclosed like that, it's even more obvious the greenery is faux because no actual plant could survive up there.

For a quick fill-in, so you can take the time to amass meaningful and coordinated objects, how about this?

Choose thrift shop or dime store pieces, probably ceramics or wood boxes or statuettes or similar, and spray paint them all a single bold accent color. Then replace them one by one as you accumulate more significant objects.

Qwan could have fun with a line up of faux resin animal heads;)

be patient, empty is better than junk. do NOT go to homegoods and bring home a cart of random. are the shelves adjustable? i'm wondering how items would look if the shelf was in the lowest position (say 2 inches above the floor of the cabinet) so you'd see the whole thing.

have a carpenter add holes if they arent low enough.

Great excuse to start a collection of something pretty that will be enhanced by the lighting.

The New American Home · More Info

I would have hung them the otherway up 1

'what are the dimensions of your cabinets? are they 42" and 18"?

you could keep the glass shelf and just place it on the bottom on the cabinet. I've done that with some wood shelves and it gave me just under 1/2" height to display an item in a glassed cabinet.