Your kitchen won't appear smaller or larger - but it will be far more useful.

Taking your eye upwards usually makes a room feel larger, especially if you add cabinets with crown molding to the ceiling over only a select number of the existing cabinets to break up the space. If you truly need a solid bank of cabinets for more storage, consider changing select door fronts to ones with opaque glass and interior lighting to break up the space as well.

@AARCON. Over which cabinets? And which door fronts in glass?

Those can really be personal taste questions. You have six cabinet sections, starting from the one over the fridge as #1 (left to right). You could add to 1, 3, and 6, or I've seen 2, 4, and 6 in similar set ups. If you added to set 1, you could also think of changing it out completely to a counter depth cabinet instead of a wall depth, maybe as a wine rack even. Changing door fronts to glass can vary with taste also. I would lean towards change out #3, the corner cabinet, and #6 on the end to glass doors top and bottom if you had solid cabinets on top or not if the budget allowed.