Requirements for the picture/photograph
Most ideal would be a digital photo with a high resolution (dpi). These photographs are best enlargeable in order to make all details visible. You can check yourself on the computer whether a picture is of good quality. If you enlarge the picture and the details still do not become blurry, it is a suitable picture. A minimum of 1.5MB should be taken into account.
If you scan a picture, do so with a resolution of at least 300dpi. In addition. a photograph should generally be clear and sharp. An over- or underexposed photo does not provide enough detail.
In general, a photograph should provide as many details as possible.
I can't draw what I can't see.