There is nothing un-nice about slapping an ass. There is nothing inherently nice about a neck kiss is there? By categorizing activity in two different columns, we make things too rigid and more challenging to employ.
There are plenty of nice guys and women outside the bedroom who can turn on some heat between the sheets. Talking dirty, or pulling a fistful of hair isn't copy written for bad people. It's copy written for anyone who wants to explore a fuller range of their sex life and more importantly if it is clearly welcomed.
And this is the greater point; if you want z, y or z in bed, don't be shy to ask for it. It doesn't make you a ho' to want your nipples pulled. It doesn't make him a monster to want his wang slapped around. My advice is, remove the labels and ask for the activities by name. Once you open the floors to specifics, see how he improvises based off of that. My sense is he will get what you are after and once he sees your reaction he'd be sexually brain dead not to continue in that direction
Eeek - I used to have this problem with previous guys I've dated until I met my now long-term BF. I think it's down to you to initiate things here, however awkward you may find it. When i first met my bf the first night set the tone for the rest of our sexual relationship. Acting out of my usual comfort zone (I thought I would never see him again - so that helped) - I asked him to do all kinds of things I would normally be to shy to say. And he took it from there :D If you don't ask you don't get - he's no mindreader.
Agree with both FG and take the plunge. He might need to be encouraged. Our society and media can give a guy the impression women are disgusted or repulsed by kinky sex, he may simply be restraining himself because he's not sure how you will react.
So tell him! Tell him what you want and how you want it. Let him know you are very open to different sexual experiences. You might need to guide him, gently, on what pleases you.