You could be a Wiccan who simply incorporates Shinto deities and other aspects of Shinto into Wicca. Wicca is loosely-organized enough to allow for that.
You can incorporate different views and beliefs into your own ideology. So yes, you could, but whether you would be easily accepted by others is a whole other but non important story. My ideology is based off of 10 or more different belief systems!
Shinto is mostly an ancestor worship religion. They really have no 'gods and goddesses'. Wicca usually focuses on a Dual Deity...so I suppose you could. It would work especially if you happen to be Japanese in origin but wish to explore Wicca, which is mostly Pre-Christian European.
It's a very personal path, what works for you works for you - don't let anyone tell you otherwise. (So glad there's positive answers here)
I always advise people to be brutality honest with themselves and follow their "inner bell". If something doesn't 'feel right' stop & look at the alternatives.
I think it is inappropriate for one to practice two religions at once, because they wouldn't be faithful to either, and that would be disrespectful to both religions.
Shinto recognizes Gods of other religions as just another Kami and has no problem with belonging to another religion. It has a continuous history of over 2000 years.
Wicca is a religion that was made up less than 100 years ago based on what someone thought the original European religions were like. This doesn't make it any less relevant to its followers, but it does make it hard to distinguish the real religious leaders from the scam artists.
If you can be Buddhist and Shinto (as many Japanese are), I don't see why one can't be Wiccan and Shinto. Shinto is a perception of the spirit world and a practice of cleansing the self of impurities. It is hard to be a true Shinto practitioner outside of Japan and the Shinto deities and spirits are sort of their own pantheon, so I'm not sure how the concept of the Lord and Lady of Wicca would mix with the Shinto spirit world, but I'm sure it could be reconciled in some way.
I've adopted a couple of Shinto style practices into my own witchcraft. It's a beautiful religion.
-Scarlet