If you have the Custom Design upgrade, you can create various mouseover effects. Here’s a solution I worked out for zooming from a thumbnail to a larger view of the image. This solution will display the larger view as a centered overlay, with the rest of the page blackened out (a-la Lightbox):
The thumbnail can be captioned or not; the larger view can also be captioned or not (independently of the thumbnail).
For live examples see this demo post. [Sorry, upgrade on that blog has expired]
Drawback: unlike the true lightbox effect, there can be no ‘close’ button (it requires types of code we’re not allowed to use on wordpress.com); so, to return to the normal view of the page, you have to move the cursor outside the browser window.
Insert the thumbnail the normal way, with or without a caption. Insert the same image again, as a full-size image, with or without a caption. (In both cases the “Link to” option should be set to None.) Then enclose the two image codes in divs this way:
If you’re only going to use full-size images without captions, paste this in the CSS editor:
If you’re also going to use full-size images with captions, add this as well:
If you wish to display the bottom note I’ve added (“hover outside browser window to close”), add this too:
• You can decrease the decimal number in the rgba background rule, to increase the transparency.
• The #222222 above it is a fallback in case an outdated browser version doesn’t understand rgba.
• The table-cell display value that is used to center the overlay won’t work in IE7 or earlier.