There are lots of simple ideas to customize your image before you use it on a blog post or as social media content. One of which, you can add a gradient overlay to your image to make it looks more artistic. If you add the gradient overlay regularly to every image before you use it, this can also strengthen your brand image or your identity.
In GIMP, adding a gradient overlay to an image is not a big deal. You can simply add a transparent layer above your image and fill this transparent layer with a color gradient. Follow the steps below to add a gradient overlay in GIMP.
First off, launch GIMP open the image you want to add a gradient to. You can do so by going to File -> Open or by pressing the CTRL+O keys on the keyboard. Once the image is open, add a new layer by going to Layer -> New Layer (Ctrl+Shift+N). Make sure to set the fill width to Transparency.

With the new layer selected (the transparent layer), activate the Gradient Tool (G) on the toolbox and set the foreground color and the background color. These colors will be used on your gradient. Also set the gradient type on the Tools Options box.

Apply the gradient to the transparent layer. To do so, click anywhere inside the canvas area (this will be the start point) and drag it to any direction. Hit enter to apply the gradient. Take a look a the screencast below.

Once the gradient is applied, change the mode of the transparent layer. You can select a mode to your liking. In this example, we use the Lighten only mode. We also set the opacity to 35.

Before After
If you are new to GIMP and want to learn advanced image manipulation techniques with this tool, you can download free images on Unsplash or Pexels.