Thanks for contributing to our forum. I have done a bit of research on the Bill Me Later option and it does not appear that it is something that an eBay seller can choose to accept or not accept during checkout. As far as I can tell, eBay automatically offers this payment option on purchases from any eBay sellers who accept Paypal and meet certain qualifications.
I did not come across any information that suggests your experience as a seller will be any different if a buyer chooses the Bill Me Later option during checkout so I believe it will be completely transparent to you even if a buyer chooses that option.
If you have any further questions regarding Bill Me Later, I recommend contacting eBay's customer support team for assistance.