Note: This guide requires WSN 7.1.46 or later.
Website thumbshots preview a website so your visitors can get a visual impression before clicking. To get these on your site, enable the website thumbshots switch at Admin -> Settings -> Switches. By default, WSN will use pagepeeker.com as the provider. This works well out of the box since there's no registration required nor limits on use. The one drawback of pagepeeker is that it watermarks the images with pagepeeker branding. If you'd like unwatermarked thumbshots, you have the option of using thumbshots.com as the provider instead (see thumbshots.com section later in this article.
In the default templates (the standard topic bit and the topic details template), thumbshots are displayed with the <div class="thumbshot">{LINKTHUMBSHOT}</div> template code. This displays a 120 pixel by 90 pixel thumbshot and styles it with the thumbshot css class. WSN offers you the freedom to resize this however you like by passing the width and height to the template variable, like this: {LINKTHUMBSHOT[500 <,> 400]} (shows a 500x400 version). Don't enclose resized versions in the <div class="thumbshot"> since that css is sized to a maximum width of 120px. Note that the source images from pageseeker are 480x360, so they should look good at fairly large sizes.
Generating, Caching and Placeholder Image
It takes a while, and some website traffic, for thumbshots to generate. After a thumbshot is requested (via viewing a page on which it's called), it gets queued and the queue is processed at an approximate rate of one for every two pageviews of your WSN site. As a result, if you have a low traffic or private testing site with a lot of topics you'll probably want to force the full generation of all thumbshots to process at once -- you can do this by going to Admin Panel -> Maintenance -> Regenerate and clicking the "Regenerate Website Thumbshots" link at the bottom. Since there's a delay between requesting a thumbshot and when pagepeeker finishes generating it, you may need to run this twice -- once to register all the requests with pagepeeker, then a second time after waiting a while for them to generate -- our suggestion is that you wait an hour between the two runs to be safe.
While waiting to be generated, or if it cannot be generated for some reason, a placeholder image is displayed. This is the templates/images_default/nothumbshot.png file, which is an empty transparent image by default unless you edit it. Once the thumbshot is processed, it gets cached to the /thumbshots/ subdirectory so that subseqent requests are instantly loaded.
Thumbshots.com Alternative
Thumbshots.com provides unwatermarked website thumbnails, but with a required linkback at the bottom of the page and a limitation on requests per month. To get these on your site, sign up for a free account. Then go to My Account -> Thumbshots Images -> Manage Plan. You'll see some sample HTML on that page, and will need to copy and paste the key (<img src="http://images.thumbshots.com/image.aspx?cid=the key is here&v=1&w=[Width]&url=[URL]" border="1" >) to the Admin -> Topics -> Topic Settings -> Thumbshots in your WSN admin panel. Once you save the key there, thumbshots will start showing up on your site. If you've previously generated thumbshots from pagepeeker, you may need to clear the thumbshots cache at Admin -> Maintenance -> Regenerage to see the new thumbshots.com sourced versions.
The drawbacks of thumbshots.com free accounts are the limitation of 5,000 hits per month (it's not entirely clear what counts as a hit but the caching should keep most people under the limit), the requirement to provide an attribution linkback on your site (WSN handles the linkback automatically in your wrapper template unless you've deleted it from there or installed an older version originally, in which case you should add to your wrapper). If you remove the attribution link, thumbshots.com will disable thumbshots on your site when their bot detects the attribution is missing.
For most people, sticking with the default pagepeeker provider is best.