Miriam Bulwar David-Hay
The main shopping street in Lodz was, and still is, Piotrkowska, right in the heart of the city. You can see what it looks like now with Google Street View, and you can find plenty of historical photos of it and of other streets in Lodz just by Googling. There are also historical photos of Lodz in the Polish State Archives website : https://www.szukajwarchiwach.gov.pl/en/strona_glowna . And in other Polish websites too. My favorite is a blog called Refotografie run by a Polish photographer called Stefan Brajter who takes photos of Lodz sites now and merges them with historical photos : http://refotografie.blogspot.com/ . (He's also on Facebook, under Refotografie.) I find that it's usually pretty easy to navigate the Polish sites with Google Translate even if you don't speak the language.
Genealogy Indexer is a wonderful site in which to search pre-war business directories (as well as yizkor books and other sources) from Lodz, and you can often see advertisements as well as directory entries: https://genealogyindexer.org/ .
Best of luck,
Miriam BULWAR David-Hay (a child and grandchild of Lodzers!),