One quick suggestion. When you want to have a "thumbnail" (smaller version) of a larger image, you should have two versions of the file. One small, one large. The way you have it right now, the browser is simply resizing the larger image. This results in much longer page loading times (because the size of the image files is too large) and causes the images to look pixelated.
When you specify an image to be 100 x 200 pixels on your webpage, the image should be 100 x 200 pixels (72 dpi). Don't use an image that is 250 x 500 pixels.