A lot of people make the mistake of adding the odd thing here or there in their garden, totally willy-nilly, and that typically has a result which makes them regretful. This situation is precisely why landscaping services exist in the first place, so that that situation can be avoided. The way it accomplishes this is by forcing you to really consider the things that you want and how you intend to use them, and then they help you to achieve the best results.
The type of things that landscapers will look at include things like; where the best place is in the garden to place a water feature (considering things like the where it would be easy to build, where it is least likely to interfere with something else and what can be done to make it blend in more seamlessly with the rest of the landscape), how and what you can do to make the overall design follow a matching scheme, and even other potential things that you can do that you may not be aware of yet.