6ft Table Mat – Picture

Hello,
I’m looking to get a custom 6′ x 2.5′ x 2mm table sized playmat made. I haven;t decided on the art yet, but am looking to just upload a picture from the web. 
I know the picture should have proportionate dimensions (rectangular), but are there any parameters of the picture that I need to look for. I’d like it to come out highest quality as possible so I’m wondering if picture quality will affect the product. Is there a minimum resolution and pixel count?
 
Thanks,
JM