Thought I'd add a few sites I built off the back of nopCommerce. All built with my own themes / grid system.
1. Eureka Golf - Original site was built on the back of nop 2.8 (I believe this was one of the very first 'show case' sites), but 'upgraded' over time, and still using 3.90. Lots of customisation, and uses .net MVC Donut Caching:
https://www.eurekagolf.co.uk/2. AvecSports - Huge amounts of customisation. Custom shirt printing preview, kit builder, 'my teams' where team managers can create a full custom team kit, then once ready, order the full team kit with individual quantities for each item:
https://avecsport.com/3. One of 12 stores, all running from a single installation. This was the first, fully responsive, nop3.00 (multi-store) in the world at the time. Currently running on 4.30, but in the middle of porting to 4.40.2:
https://pompey.clubstore.co.uk/Each of the club stores has its own individual theme, templates (including email templates) too.