There is so much in Himachal to explore. hill stations like Shimla, kullu manali, dharmshala, Mcleod ganj, kasol etc. which are famous and bit over crowd during the season. you can go for trekking, camping, river rafting at few places. Himachal is also called Dev bhoomi which means you can visit temples. not to mention one thing which is common in most of main cities if Himachal is mall road where you can buy some local souvenirs like jams, wines(@ very reasonable price), wooden products, woolen products, dry fruits etc. My personal favorite is to go to unexplored parts of himachal which are less commercially and less pollulated and less crowded.
Himachal Pradesh has amazing places with beautiful landscape. However, many of them would be super crowded and hence you might not enjoy much. I'd say, visit Narkhanda, Kalpa, Spiti as they're not quite famous like Kullu Manali and so you'll enjoy it more! 😁 If you're going to Narkhanda, do a trek to Hatu Peak