When learning about Adobe InDesign, we were taught the difference between copying and pasting images from the internet and using the place tool. In looking into this deeper, as designers we should consider the differences between taking images off of, say, Google and using our own work. There are pros and cons for both.
By creating our own work, i.e. photography or illustration, we will have more to take credit for. We can also control the quality of the image more than we can if we copy and paste from the internet. From the internet images can be distorted or an image that we like can be at a resolution lower than we need. Secondary sources can be very convenient though.
In considering this, we must question how much credit we wish to take for our own work. If we specialise in just layout design, then it is fine to use other people’s works, especially if, when employed you would work as a part of a team, and it would just be stepping stones for working as a team if we used alternate sources now.