Folder thumbnails are too small

[Crabbing0320]

Hello, how may I view bigger images on thumbnail folders? Zooming further than this just adds margins to the folder around it and doesn't really provide much zoom
"Normal"
Zoomed in:

I'd like to see the folder thumbnail to see the images tad better, either by making the folders bigger and not the marging around it, or have it show only two images but zoomed in or so.

Thanks!

[xnview]

do you have tried 'rebuild thumbnails'?