So, what are the most popular ones?

Heated window seats for cats to perch on and stay warm while they look out the window. "Chihuahua-height windows" are also popular - in other words, windows that start very low to the ground - so small dogs can see what's going on outside. Veterinarians say that dogs get anxious if they hear noises and can't see where they're coming from.

For cat-lovers, it's all about the catwalk. Those are cushioned ceiling beams that cats can lounge on. Experts say that cats feel safe when they can peer down on the activity going on in a home. When it comes to the kitchen, special "feeding stations" are a big trend. Those are low to the ground cabinets to store food and treats - often with a built-in sink that dispenses filtered water to fill bowls.

Another big trend is dog-washing stations, typically near the back door or laundry room - with tubs just for pets, and drying platforms for grooming.

And clover lawns are a huge hit with dog owners. That's because clover doesn't turn yellow from dog urine.

One last way homeowners are accommodating their pets - is with flooring. Bare floors can be too slippery for dogs - especially elderly ones. So owners are installing dog-friendly flooring like concrete, or applying an epoxy finish that gives dogs more traction.