The Internet is a great resource for images, but it can be annoying when images have large white backgrounds behind them. This simple trick in GIMP will get rid of the background meaning you can use your images on any background you want.
To start off, you will need to open your image in GIMP and go to Layers > Transparency and select "Add Alpha Channel". This will make it possible to actually remove the background of the image, instead of just making deleted parts of the image white.
Next, select the "Fuzzy Select" tool and click the background of the image. You should see black and white dots marching around the edge of the image.
Once you are done with that, just press CTRL+X to delete the background.
And now you are finished. You will need to export the image as a .png in order to save the transparency, otherwise, the background will just come back.