Almost all launcher have the option of changing the app icon to another image.
If you are using a launcher that does not support this option, you can use the app called “Desktop Visualizer” to use different images for your apps on your Homescreens.
1. Lon press the app on your homescreen that you want to modify
2. Select replace
3. A new window will pop-up with the icons from the current theme you are using. You can choose one of this or select the menu on the top left to choose a different set of icons from another installed theme.
4. Select the new icon image and that is it!
You can also select an image from your gallery.
1. Click on the gallery botton on the top right
2. Scroll to the folder where your image is, and select the image
3. A crop option window will pop-up. I have noticed that the icons looks a lot better when I select the No Crop option.