Tenpura is just food that's been deep fried in tenpura batter. You can buy the batter flour from most shops these days, just follow the instructions and use it to coat whatever you like..!
Literally, almost ANYTHING can be used for tenpura - they prepared tenpura of watermelon skin on TV the other day, and a bunch of elementary school kids sampled it and said it was delicious..!!
Generally, prawns work well, so do bits of squid, most vegetables - though the ones that take longer to cook, pumpkin, potato etc. will need to be cut more thinly. I had Ten-don yesterday, a big bowl of rice, with tenpura on top - a big prawn, squid roll, green beans (the longish green beans that are round if you cut them across,) Japanese pumpkin, and a small filleted fish! Very nice, but I can't tell you what it was that YOU ate at that restaurant I'm afraid...!
By the way, here in Japan I've never heard of anyone using wine in their tenpura batter - or eggs! That doesn't mean that no-one uses them, it's just that it's not routine. Putting eggs in it would make it taste wrong! It would probably end up tasting like you were eating British fish and chips...!