A couple of stops I discovered in searching for landscaping ideas.
First off Alices Garden.
This place is amazing the designs textures and original thinking that is created here is well worth your visit, even if just appreciating a beautiful setting.
The other place I discovered to my great delight (and vast depletion of my lindens) is forest feast fantasy garden. This is one of the most gorgeous sims i have ever seen. The creator and designer is pure genius. Just visit it for the most beautiful meditative experiences, but be warned don't leave you lindens behind, you will want to purchase many of the creations there.
Basically I was just overwhelmed with jealousy, wanting to buy the whole sim as is