I'm trying to think of how I should design a place for Sims to shop, as well as what to sell. I want the atmosphere to uplifting and happy. Do you have any ideas?

Did you look over my thread (3/4 down the front page here) https://www.modthesims.info/showthread.php?t=561271

I bookmarked this thread for when I need ideas, then I do research on Google to see how they look/function.
For an example: I'm planning to have a sim with a vineyard (from PBK), then I'm going to have them buy a pub from the Little Britian section of
my neighborhood. I'm planning to have them sell the resulting wine there (and also use bienchen's community lot revolution to sell drinks and have mixed appetizers)

EDIT: spelling

If you want an atmosphere that is uplifting and happy, I suggest you go ham on Michelle's countless LACK-recolor uploads. Her recent recolors of the espresso-stand for community lots has me wanting to build a sort of 50s diner, because the LACK colors give such a happy upbeat feel compared to the drab wood of Maxis colors.

Are you thinking OFB-shop or do you mean stuff like groceries and clothes that Sims can by on their own? If you mean the latter, I'll shamelessly plug my own Sunnyside Mall upload. It's one of my least successful uploads, but I love it to death. It has all the things Maxis allow us to sell without a Sim owning it, and I love the atmosphere. Maybe you can find some inspiration in one of the shops

If you're thinking OFB-selling, and you're not sure what to sell, I would start by asking yourself, what does your Sims need? And would you actually go to a community lot to get it? I have a few warehouses that sell buy mode stuff, like a huge child store that sells toys and everything your Sims need to have children, as well as an IKEA-style thing that sells furniture. But quite often if my Sim needs something, I'll have bought it from buy mode catalog before I had time to think, so most often I don't end up going to those stores. So the lots I am most likely to use, are the ones that offer things I can't get in any other way. For me, that's gardening produce, clothing and jewelry. I also like ticket-businesses, the one that's getting most use at the moment is the laundromat.

I recommend checking out my list of things which you can find here:
http://simlishnoir.tumblr.com/post/...n-your-citytown