preview image make up

Hey guys

I assume my questions are css related so I will post them here, please let me know if I'm wrong.

On my website I use the following code

{g->block type="imageblock.ImageBlock" blocks="randomImage" maxSize=100 showDate=0 showOwner=0 showViews=0 showTitle=0 showHeading=0 useDefaults=0}

to create random click able images (previews), see http://www.sjoukito.com/album/v/country/

I am wondering if it is possible to only use the horizontal and not the vertical images as preview using css or something?

Or even better could we set a fixed with and height for them, so that would be something like this I guess:
{g->block type="imageblock.ImageBlock" blocks="randomImage" -------->maxHeight=100 MaxWith=100<---------- showDate=0 showOwner=0 showViews=0 showTitle=0 showHeading=0 useDefaults=0}

The second question I have is if I could give these random preview images (and only these images)a white border like one could normally do with css with the code Border: 3px solid #ffffff;?

Thanks for the help,
John