First of all you refer to the production of fully hand-drawn, or PS Taobao like pictures.
Fully hand-drawn for hand-drawing, line drawing requirements are very high.
PS Taobao pictures like that is relatively simple. The main thing is to key.
Open PS, create a new file, set the image size of 800x800 pixels (see chart for detailed parameters).
Prepared baby pictures dragged into the PS inside. Adjust the size of the baby pictures so that they are evenly lined up on the page.
Click File - Store as web and device used format, set the parameters, format selection JPEG (detailed parameters see figure) Click Store.