Glad you asked! Don't know that it has come up before. Or if it has, it was a long while ago!
You can make your own image. Or one of us can help you with that. What you ask is relatively easy.
We just need to know YOUR dimensions.
How much needs to be white? Then where will you like the GRAY to be? Then the rest would be fade to black.
Click here to see a sample 808 pixels wide.
You would grab the image and store it on YOUR computer by right clicking it.
Then open CSB
Set the background image as the new image. Check the box to tile VERTICALLY. This will force a repeat of the thin image to fill the page from top to bottom.
Also right click the page, Properties, Page, background tab and choose BLACK as your main color for the page.
The background image ALWAYS loads from top LEFT of the screen but the visitor is using a monitor set to a wider resolution, the rest of the page will blend if you set it to plain black. This will mean that anyone with a wider screen will have the right side filled with black.
(By the way, I MERGED your posts into one thread. There is no need to CROSS POST (post in more than one area of the forum) about the same issue. Those of us that help out read all the areas. Makes it very confusing if the help is split into two or more threads instead of all together. Then I moved the merged thread to the CSB section for better organization.)