Change size of thumbnail, Theme:Thanks Roy

how can I change the size of the thumbnail picture and maybe also the placing?
right now the thubnail is a litten bit too Small, and it would be nice if it coul be placed next to the text not underneath

On what page do you want to change this?
Thumbnail size for the entire Omeka site can be changed in appearance settings; you will want to run derivative images after you change these settings.