table.wp-list-table td.column-thumb img {
 
    max-width: 32px !important;
    max-height: 32px !important;
    
}

table.wp-list-table td.hoverimage img {

   max-width: 30px !important;
    max-height: 30px !important;
}

table.wp-list-table .column-thumb {
    text-align: left !important;
    
}