I was recently out with a friend when he showed me some of his work on Flickr. What immediately struck me, other than how good his images were, is that they had a consistent look. All of them had a nice clear white border around them as well as a thin black Keyline. This made all the images really stand out against the dark background of Flickr.
The process of adding the border is done in Photoshop where the image is also resized. If you would like to see what this looks like on Flickr, I have uploaded an example. I would also suggest you take a look at my friends work here.
If you decide that you like this technique and want to know the steps I have prepared a free tutorial on my Lenscraft website.