Do what I did for 247's site. Put a folder of thumbnails into Domain.com/Images/Thumbs/ for each thumbnail, have a standard prefix. Such as T_Image.jpg
Where you link your images, change the link to be:
<a href="src="Images/Image.jpg"><img src="Images/Thumbs/T_Image.jpg"></a>
as apoosed to
<a href="src="Images/Image.jpg"><img src="Images/Image.jpg"></a>