I’m good enough with CSS just to modify and only if the developer does proper commenting. My suggestion is to keep to landscape images. Crop them if you have to beforehand. Obviously the developer intended to keep this theme simply. I’m sure there is a way though but it would probably be in java code and not CSS.
Glad it worked out. Discovered this theme recently to use for my vacation website. Loved everything about except for the tiny lightbox images. Was about to give up until I found the way to change it! 🙂
Like inphra mentioned. If you have existing images in the gallery, remove them and reupload them all. Otherwise the updated size won’t register.
Took a couple days digging thru the code but I found it. Open grid.css in the css folder. Go to line 197. Change max-width to a percent or a larger px size. I used 1024 and it looks much nicer.