I dont think there is a tutorial for that "type" of picture, its more or less just knowledge of a graphics program that supports layers etc
You have various layers containing pictures and lines and gradients, and you will play with masks and or the eraser tool, paint brush and opacity levels and more. Some what simple to come up with if you know the tools
Using pngs all the time is just as silly as using jpgs all the time. They each have their own duties in the graphics world. Sometimes, often, jpg is the right format to use. That doesn't mean I have to like them.