(Edited 6-20)(Don't worry, this post won't be as long as the last one)
I believe there have been discussions about this on the site before, but I've recently come into contact with a lot of photos that have borders in the Art Council voting booth, images which I voted not to be added to the permanent galleries because the border was distracting and unnecessary. IIf I'm on the fence about an image, I look at the image on a desktop. More often than not, the image looks squished on the screen because the top border is pushing the image downwards because the bottom border can't be seen because of my taskbar.
There are some situations where borders are a good thing (like making it where an image can fit desktop dimensions), but in general borders detract from rather than add to an image. Especially as a background site, artists uploading images should be aware that borders around the perimeter of the image make the image off-balance on the screen. The reason is that the top of the border squishes the image towards the bottom because of the taskbar, which covers the bottom border. Instead, make sure that your images are great when you take them; if you feel the need to add a border to your image to "spruce it up", then you probably don't have a great image.
If you are concerned about adding a border to allow the image to fit the desktop size, I would suggest generally using only black or white, because the color should come from the image itself. Having a landscape photo with a green panoramic border is very distracting to the eye because everything's green and the eye has nowhere to focus.
While borders, like art, are a matter of taste, I think there are certain rules that apply to it. Here are some examples of good versus bad background borders:
(The image is a stock image and isn't great on it's own, as Sam points out below, but these are the type of images that I typically see with colorful/textured borders.)
The first example is distracting from the image: it goes around the perimeter, it has texture, and it has color. The second border enhances the image: it is black, it is panoramic, and it is simple. In my own rule book, borders should be used almost exclusively with panoramic photos and not with full-screen images. There are some borders in between that I think can still be tasteful and elegant without being overpowering. For example, if you choose to do a panoramic image but feel that the black border is boring, try adding a thin line at the top/bottom of the border of any color taken from the image. This gives it a little pop without overdoing it.
I believe there have been discussions about this on the site before, but I've recently come into contact with a lot of photos that have borders in the Art Council voting booth, images which I voted not to be added to the permanent galleries because the border was distracting and unnecessary. IIf I'm on the fence about an image, I look at the image on a desktop. More often than not, the image looks squished on the screen because the top border is pushing the image downwards because the bottom border can't be seen because of my taskbar.
There are some situations where borders are a good thing (like making it where an image can fit desktop dimensions), but in general borders detract from rather than add to an image. Especially as a background site, artists uploading images should be aware that borders around the perimeter of the image make the image off-balance on the screen. The reason is that the top of the border squishes the image towards the bottom because of the taskbar, which covers the bottom border. Instead, make sure that your images are great when you take them; if you feel the need to add a border to your image to "spruce it up", then you probably don't have a great image.
If you are concerned about adding a border to allow the image to fit the desktop size, I would suggest generally using only black or white, because the color should come from the image itself. Having a landscape photo with a green panoramic border is very distracting to the eye because everything's green and the eye has nowhere to focus.
While borders, like art, are a matter of taste, I think there are certain rules that apply to it. Here are some examples of good versus bad background borders:
1. Not-so-good Border
2. Decent Border
(The image is a stock image and isn't great on it's own, as Sam points out below, but these are the type of images that I typically see with colorful/textured borders.)
The first example is distracting from the image: it goes around the perimeter, it has texture, and it has color. The second border enhances the image: it is black, it is panoramic, and it is simple. In my own rule book, borders should be used almost exclusively with panoramic photos and not with full-screen images. There are some borders in between that I think can still be tasteful and elegant without being overpowering. For example, if you choose to do a panoramic image but feel that the black border is boring, try adding a thin line at the top/bottom of the border of any color taken from the image. This gives it a little pop without overdoing it.
Please feel free to add anything to the topic...