Being a photographer for well over 60 yrs from box brownie your question is very familiar. IMHO a background should do several things but for me with pens I use 11 by 14 inch photocopy paper this one ream has served me for twenty plus years, my set up takes me fully five minutes to have ready, lit and in business, it is an open frame of conduit with two pieces on top to support a top light as well.
Neutral grey is an ideal for white balance.
Keep your background out of focus, have back lighting to help separation. For me sometimes I get carried away and throw in timber offcuts, shells indeed anything just a few thoughts mate from a bloke who bought three hundred fabric samples one time to use as backgrounds and came back to a simple solution that suits me.
have success Kind regards Peter.