If you download an image manipulator you can resize them to the suggested 1000 pixel width for LAF.
GIMP is completely free and is more than adequate. In fact it's got loads of functions I've never even used, but as well as resizing I often use it to adjust colour balance and brightness for example.
Although it is completely free, it's always nice to make a little donation to support the folks who develop and constantly update this and other free ware, you'll see the link whan you download
