Each room a different theme, would it look tacky?

Maybe he would feel better about the themes if you kept all the walls the same color. I hate to use white everywhere it just seems too stark and sterile but that might be what would make him more comfortable or maybe he would be okay with an off-white.

You can create the theme of each room with decorative accents, curtains, pictures, rugs, doodads sitting around or on shelves, type of furniture, etc.
Blues, tan and gold for a beachy feel with maybe a white wicker chair or tables, shades of greens and browns for a restful forest feel, etc.

Since guests usually only see the livingroom, kitchen, diningroom you might keep those more of one style to blend together but you can still have a theme for them with the accents and colors.

Bedrooms can be fun to decorate, kids know what they like in colors, etc. Your bedroom should be a retreat that is comfy in color and decor that you both like.
And they have doors that can be closed when company comes. If their opinion is important to you then you don't have to let them see how you choose to decorate your private spaces.

 

Please post before and after photos of your makeovers, we would love to see them.