I am looking for the same thing, but cant seem to find the answer anywhere in the arcade skins files.
Mr Zeropage??
--------------- Added 1218967950 at 1218967950 ---------------
At last, ive found it......
In arcade.php around line 2064, find
$the_cat['cat_name'] = "<img src='".$file."' alt='' border='0' width='20' height='20' /> ".$the_cat['cat_name'];
And obviously change the 20's to 50's.
Ive also atered the bit in red for a <br />, so the name of the category is below the image.
If you want to put the amount of games below the name of the category, look on the next row down.
Just before (".$the_cat['num_of_games'] add a <br />.
It just looks neater.
Hope this helps :)