You should have heard of adding watermark to Word documents, but you can do the same in Excel files too. You need to do this manually and I will explain here how it can be performed.
Open your worksheet in Excel and click the Insert tab on the Ribbon.
In the Text section, click Header & Footer.
The Header & Footer Tools Design tab displays. To insert a picture as the watermark, click Picture in the Header & Footer Elements section.
The Insert Pictures dialog box displays. Select the location where the desired image file is located. We selected an image from our hard drive, so we clicked Browse next to From a file.Navigate to the location of your image file, select it, and click Insert.
To view the picture behind the contents of the file, click on any cell outside of the header. You’ll notice that the image displays behind the text and graphics in your file, but it is full color and possibly very dark.
You can easily make the image appear faded. Open the header again so the Header & Footer Tools Design tab displays again. Click Format Picture in the Header & Footer Elements section.Click the Picture tab on the Format Picture dialog box and select Washout from the Color drop-down list. Click OK.
The picture becomes faded behind the text and graphics.
To remove the watermark, simply open the header again, select the text or the picture marker (&[Picture]), delete it, and click in any cell outside the header to save your change.