By adding STYLE="BORDER: RED SOLID 4PX;" to your image HTML you can make the image have a red border (or any other colour you choose).

Here's the HTML

<IMG SRC="http://www.yourimagehost.com/yourname/yourpicsname" STYLE="BORDER: RED SOLID 4PX;">

And here's how it looks-

Or

<IMG SRC="http://www.yourimagehost.com/yourname/yourpicsname" STYLE="BORDER: #0000CC SOLID 7PX;">

You will find a Colour Table by clicking here