1. A computer-implemented method, comprising: determining, by a computer system of an electronic marketplace and based at least in part on a generation rule, a particular number of images and particular size ranges of the images for presenting information about a plurality of items offered at the electronic marketplace; generating, based at least in part on one or more source images, a number of item images having different sizes for an item of the plurality of items available at the marketplace, the number of the item images equaling the particular number, the different sizes of the item images meeting the particular size ranges; generating, by the computer system, a network document associated with the item, the network document comprising a placeholder for displaying an item image from the item images, the network document identifying the item images and the sizes of the item images, the network document comprising a script for selecting the item image from the item images based at least in part on a size of the placeholder; providing the network document to a computing device of a user; receiving a selection of the item image from the computing device of the user, the selection based at least in part on using the script to compare the sizes of the item images to the size of the placeholder; and providing the item image to the computing device of the user, the providing causing the computing device of the user to display the item image in the placeholder of the network document.