Backyard water parks. Hedges shaped like animals. A six-person Jacuzzi bath with mood lighting.

When it comes to adding value to a high-end home, an amenity with a large price tag doesn't guarantee a return on investment. Sometimes, a customized modification can actually reduce a home's value.

But that can be a tough sell to high-end homeowners.

"If they have sought out a unique feature, and paid for it, they think it's valuable and will overprice the home because of it," said Brendon DeSimone, real estate expert from Zillow.

Over-the-top features and customizations can even degrade a luxury property to fixer-upper status.

"I once saw an apartment in the city with Venetian plaster on all the walls. The new buyer would have to take it all off. That comes with a cost," said DeSimone.

Here's a look at luxury home customizations that might not be worth the investment:

Ornate landscaping

Strong curb appeal is a must, but there's a limit to just how far to take landscaping.

"Today's buyers want a cleaner cut yard and landscaping, they don't want all the fuss with multiple trees, shrubs and bushes," said Bo Mastykaz, a luxury real estate agent in Miami. "They don't want to feel like they're in a jungle."

Related: 5 luxury amenities wealthy homebuyers want

Elaborate outdoor pools

Turns out, not everyone wants an amusement park in their back yard.

"Elaborate rocks fixtures, slides and waterfalls may be nice to look at, but may require a lot of maintenance and safety can be a factor for some buyers," said Jud Henderson, broker associate at Sotheby's International Realty in Princeton, N.J.

Be warned: If you're thinking of adding a pool, it takes a long time for the investment to pay off.

Huge tubs in the bathroom

Gone are the days of needing to host a party in the bathroom.

"Most modern buyers want a normal-sized bath tub and a large shower, there's no longer the desire for a six to eight person Jacuzzi in the bathroom," said Mastykaz.

He added that overspending in the bathroom tends not to bring a strong ROI, but one upgrade that's worth the money is walling off the toilet. "When it's out in the open, that's a definite draw back."

High-end materials

Imported marble might cost a pretty penny, but it could also be a deal-breaker for a potential buyer down the road.

"It doesn't matter if it was flown in from Italy or Spain, a lot of today's buyers think it's too ornate, especially the size of the tiles," said Mastykaz.

Even the once-popular granite is falling out of buyers' favor. "Quartz is less busy and more minimalist and it has a natural sparkle finish that buyers want."

Related: No end in sight for New York's multimillion dollar housing boom

Using too many colors for the cabinets, tiles and floors and can also turn off buyers. "It's difficult for the vast majority of people to envision living in a highly expressive space or anything outside a more neutral color palate that they can then add their own personalization to," said Dean Jones, CEO of Realogics Sotheby's International Realty in Seattle.

Too much automation and security

While luxury homeowners want to be able to control their home's features remotely, the technology still has to be manageable.

"They want to touch one button to have all the lights turn on and off and control the temperature," said Danny Hertzberg, luxury realtor with The Jills of Coldwell Banker Miami Beach. "But when the showing agent can't work the system, the buyer isn't going to want to bother."

Security tends to be a top-priority with million-dollar homeowners, but too many cameras can become creepy, Mastykaz added.

Oversized rooms

Taking away a bedroom to create a larger room or re-purposing it into something like a wine cellar or recreation space will likely reduce a home's resale value. "There's a reason the first thing typically detailed on a home listing is the number of bedrooms," said Jones.

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Another no-no, is converting a garage into a living space.

"Buyers spending $10 million on a home have a lot of toys that they they're going to want to store," said Hertzberg.

The man cave

A special room for the man of the house is so 2010.

"No husband that I have taken out in the last three years has put an emphasis on that," said Mastykaz. "And women just disregard it and have it changed."

Screening/media room

With today's large screen technology, media rooms have become old news.

"These are definitely out, especially those with projections screens," said Mastykaz. "When you add in the stadium seating and everything else, it feels gimmicky rather than true value to buyers and they will pursue something else."