Limit user specified forum image to be no larger than forum link icon

In ACP->FORUMS->Edit forum one of the Forum types is "Link", which allows the admin the opportunity to specify a Forum image  of an additional image to associate with this forum. 

The forum image is displayed is displayed beside the forum_link.gif (which is downsized via CSS) but there is no constraint on the forum image, so it is displayed actual size. 

An improvement would be to limit the displayed forum image size to no larger than what is displayed for the forum_link.gif, making them consistent. 

This would be particularly helpful if a SVG image is being used so that it scales nicely on tablets and smartphones.