I once wrote 15 love letters, stuffed them into balloons, blew up the balloons, and left them in the bathtub with the shower curtain drawn. When my dude came back from being out of town for two months, he found them and was deeply moved. He still has those letters in his underwear drawer today.
We had a great view from our balcony in MA. I would sometimes make a picnic, and set it up out there with music. It was nice.
I purchased some large, flat lava rocks, and a book on hot stone massage. A few times a year, I wake him up with soothing music, and give him a full-body, hot stone massage, with happy ending. It takes me about 90 minutes. I recommend using a hotplate and a huge pot of hot water to keep a steady rotation of hot rocks available.
When we go to NY, I like to take him past a certain area, and point out, "That's the spot where I fell in love with you. Remember? Remember what happened when we were standing over there? I love you."
I write email to my husband while he's working. I just let him know what's going on in my day, ask about his, find out what he wants for supper, and if he's going to come home wanting a snack. Sometimes I'll just send a joke and a reminder that I miss him and want him to come home ASAP. He likes these things, and if a few days go by without my writing, he'll ask me to write as he's on his way out in the morning.
I called his mother and got recipes for his favorite meals. I make them my way, but he knows this is a gesture of love when I'm making his favorites.
He once surprised me with tickets to a great show, and took me to dinner. It may seem cliché, but it was very romantic to me.
Valentine's day, I plan to order him sweets from his favorite shop in NY, a place I originally found for him as a romantic gesture, based on his obsession with all things Japanese.
My ideas for romantic gestures come from intimate knowledge of the man in question. How can I incorporate a selfless gift of time, attention, or materials into his interests? That's the question I try to answer when I want to be romantic. For example, for our paper anniversary, I gave my video game addicted, history buff husband a calendar of antique maps, and a deluxe version of a strategy guide for a game he'd pre-ordered. (Actually, I had to make him a voucher for the guide, because it too had to be pre-ordered.) He shows everyone who comes over.
You know your man. What can you do to show him that you know him? That's the question you have to answer.