Help with texture mapped parts

[Jaco van der Molen]

A few examples attached...

And part 13459:
LegoRoad Sign Round on Pole / ROUND SIGN 1X5X3

This one is not subparted (it's clearly made for stickers), so I had to subpart it...

The sign: one on one side and one both sides :-)
Pattern print on the round piece of course.

Made only a double sided one. For a single sided, remove the texmap stuff of one section, leave only the content of fallback.

Do the PNG files need to be rectangularly shaped with white or transparent background?

Doesn't matter if it is outside the surface onto which it is applied. Note that I left a transparent window in the image to let the color of the part see through.

Ah, OK, I see. Many thanks.
I will study these parts.

As for the part number of the nexo shield tile part and its aliases: does it really matter what part I use?
I think this probably has something to do with solid plastic and color and transparent ones?