Help with - "@tik" Categories with thumbnails 1.1

I am currently using the "@tik" Categories with thumbnails 1.1 extension.

Its working perfectly fine, so "thumbs" up to the creator! (pun intended)

Although I would like the images to be bigger, I can see where I can edit the thumbnail size in the xml code, but when I do, the images overlap, instead of dropping to the next line.

To change this, do I need to add more code to the xml file? Or do I need to change some CSS?

Any help would be greatly appreciated.

Thank you