Alkivia thumbnails

I would like to know if it’s possible to use different thumbnails for the gallery and for authors in the posts.

Having to use the same size don’t work….Gallery photos are too small or auhtor pic in posts is much too big.

I know I probably would have to change something in the css adnalso in teh code? A hint on this would be appreciated.

Also how can I exclude author thumbnail in one category only?

Thank you!