I have made comments on the code, as to where you need to make changes to accommodate more images.
iNumOfImg = 3
Change this value, depending on how many images you're planning to put up.
image bounds(64, 160, 82, 71), identchannel("imageIdent1"), visible(0)
image bounds(178, 158, 85, 77), identchannel("imageIdent2"), visible(1)
image bounds(64, 160, 82, 71), identchannel("imageIdentX"), visible(1)
Name the identchannel fields in this manner, for all X number of images.
Take a look at the code in detail. Shoot, if you need more info. Also, please edit the title of your post to something more appropriate like "Switching images on and off using slider" or something like that, so that it could be of help to another person who is browsing through.