Make a custom PC desktop wallpaper by using an image editing program such as Adobe Photoshop or GIMP to create new graphics or modify an existing image, such as by changing its colors or adding text. Use the programs to change the size of the image to match the resolution of your monitor.
Begin by determining the optimal resolution of your monitor by opening the Control Panel and selecting Adjust Screen Resolution from the Appearance and Personalization tab. This menu displays the length and width of your current monitor display in pixels. Next, decide if you want to use an existing image as the base for the wallpaper or if you want to create an image from a blank canvas. If you are modifying an existing image, open it in the image editing program of your choice. Alter the image size from the Image menu so that it matches the exact dimensions of your monitor; you may need to constrain its proportions to avoid warping or stretching the image.
Use the painting, text, shape and effects tools of the editing program to alter the image as necessary. Many programs contain a layering feature that allows you to combine multiple elements independently. When you're done, save the image as a JPG or PNG file, then open the Personalization section of the Control Panel and set the image as your wallpaper.