Technically nothing, because I don't believe romance is truly possible with animals.
I'd say the things you mentioned, but regular animal owners do the same so it's hard for me to say it's romantic.
When I feel the most romantic with her it's when we're both really in the mood and when she shows obvious affection.
Could also be just laying in bed with her, eating icecream together, or even some sexual contact, things like that.

The great thing about animal romance is that I don't have to make great gestures, I don't have to spend lots of money.

It's the little things that make our time together special.

Just snuggling anywhere, going for a walk and watching him enjoying himself. Seeing him after getting back and knowing he will be happy. Spending just 5 minutes makes us both happy.

Romance really doesn't come into it as it doesn't require it. Knowing we are there for each other is good enough for both of us.

Romance is mostly a human thing, so i substitute things like close contact interaction( like playful wrestling, snuggling, sleeping in your lap (or vice versa?) ), going out to non typical locations with each other, or just going outside your norm in the name of love.

But some animals just arent romantic in any reasonable sense, and thats ok.

Camping for sure is like the best. Dog curled up to you falling asleep as you tend to the slowly shrinking fire, or waking up to them nestled tightly against your chest through the crack in the sleeping bag, and you decide that maybe you can sleep a little longer, or taking that morning walk and maybe even sharing that morning pee haha.

Any time with them and nature is like hella bonding time. But also I like playing tug with them or laying next to them and watching them chew on their toy or other lame stuff lol.