Quick disclaimer, I did not make and do not own any of these, I have simply collated various images I think you may find useful for designing your own Mandalorian armor.
Basic armor template (I edited it for ease of fill bucket use [if you use Paint.net, I would suggest a tolerance of 40%], and I decided to color in the belt because I had to adjust it anyway. If you don't like it, it should be easy enough to change).
Basic helmet template.
Nite Owl helmet (this is a picture from a 3D printing template so I'm adding the Etsy link): https://www.etsy.com/listing/661353783/3d-printable-helmet-inspired-by-ursa
Mandalorian symbol.
Mandalorian Protectors symbol.
Mandalorian Nite Owl symbol.