You can't do that, since the page you're requesting does not give you a directory listing. Ie: the wildcard can mean anything, but you don't know what if it could be. For example, in your example, it could be: 2a.jpg 2b.jpg 28489ch7833.jpg 29478947893jhchf748hf4.sdy893nfd.213.jpg
And each of those would be an HTTP GET. You'd quickly be banned/blocked from whatever site you're grabbing those images from.
The only way is to grab all the HTML/CSS and grep for references to '2*.jpg', and grab those files. That does not obviously get any files that are not referenced in html/css