Use reasonably sized images
The biggest performance lag comes from using really large images and letting the theme script scale them down for you. This might work OK in your local environment, but it can have great effects for users with less optimized setups and slow internet connections.
Always scale down your images to a reasonable size and use jpg for compression. Image Quality
A good standard to start with is 600 x 600 pixels using 70 as quality.
Other standard sizes for landscape images would be:
• 1024 x 768 pixels
• 1280 x 960 pixels
Compress your images
Another good procedure would be to compress your images prior to uploading.
There're several image compression software available for the Mac, I use JpegMini with great results: http://www.jpegmini.com
Don't add too many images at once
There are no limits to how many images you can add, but after 30 it can clog the pipes on load, especially in slower browsers like Internet Explorer.
Use a reasonable amount of images at first, then try the check/uncheck method on Rapidweaver Album to remove or add images on the fly.