NL100 J3s

Fold preflop!
You're OOP and he's very likely to call you with a dominating hand.
As played I'm playing it the same way you did (bet flop&turn), but I think given that he probably floats most Ax, the turnbet is kind of close.
On the river it's a c/f to me, too.

But don't you think it's ok to throw in some just randomsuited hand or whatever, at an early point in a HU match to establish an aggressive image? Also, since it's is early and he doesn't know about my 3betting tendencies he shouldn't be too inclinded to call light either.

Well I'm not sure about nowaday's general HU approach, but when I'm starting a match I generally play SD bound and would call a decent range preflop, especially since a lot of people overdo it a lot with the 3betting.

And "establishing image" is never a good reason for a play, the first and foremost consideration is the EV.
And imo it's pretty negative here especially since we have reverse IO's.
If you think you can make up for a 5BB or even 10BB -EV spot by exploiting his overadaption vs your perceived loose 3betting-range, then it might indeed be a good 3bet, but imo it's quite unlikely.