Unless you have enough artistic skill to draw a card illustration yourself - in which case, you're away - you'll need to hunt out suitable clip-art. There used to be more clip-art packages around than there are now, but you can still find good libraries with thousands of images for a few pounds. Try the £10 software stands in Staples or PC World, or look at products like Avanquest's Art Explosion.
If you want free clip-art, beware of sites offering Royalty-Free clips. This doesn't mean you don't have to pay for them, just that it's a one-off payment, rather than a per-use royalty. A good place to start is the Open Clip Art Library, which has around 7,000 images completely free.
If using bitmap clip-art, with file types like jpg, tif or png, don't stretch an image too much to make it fit the card, or you'll start to notice jagged edges to lines and curves. A good rule is not to enlarge an image to more than double its ‘natural' size. By natural size, we mean the size that its resolution dictates. You can see what this size is in Page Plus by doing this:
1. Click Picture, From file on the Insert menu and browse to the clipart you want to check.
2. When the file has loaded, the mouse pointer changes to a plus sign and rectangle. Rather than stretching out a picture frame with this tool, just double-click anywhere on the page and the clipart will be placed at its natural size.
Once you've selected a clip, insert it and adjust its size - if you enlarge or reduce a picture frame using its corner handles, it'll maintain the frame's aspect ratio and you won't get elongated or squashed images.
Many clips are produced in black and white only, but this needn't prevent it being used in colour on a card. Once the clip is imported, its main colour can be changed by selecting the Swatches tab in the panel on the right, clicking the fill icon and selecting a colour from the palette.