As the NetSuite with Salesforce integration provides you with all the data about your products being purchases by specific customers, you can use this data for the purpose of cross-selling and up-selling.
For cross-selling, you can look for the customers making frequent purchases and approach them for selling them a different product (or a different variant of the same product). If you are willing to up-sell, you can approach some of the loyal customers and the high-spenders for upgrading their purchases and going for a better product/service provided by you.
Now that you have complete data about the date, time, and type of product purchased by all your customers, this data can be used to leverage your marketing and sales for improved results.