@tonbags.... I am trying to keep my teacup collection within reason by only having cups I use. I use different pots and cups for different kinds of tea. My collections are never terribly precious though my favourite teacups are made with real bone china ( new ones are no good, and new teapots don't pour properly). I think its a little different from the sort of antiques collection which takes it into a whole other league.... those sorts of collections take 2 approaches I think. 1. An investment. You are collecting with the value of the objects in mind. 2. Preserving history. You are collecting with a sense of duty to preserve the history and story around the object. If its that sort of collection I think its fine to go all out! Have a whole wing of your house for the collection then donate it to a museum or sell it at an auction!

I am at the final stages of the plan design of my house, I have probably spent 8 months in planning this home and I think I have everything covered, but sometimes you look at something so much that you actually miss "the elephant sitting in the middle of the room" I think we have made the most of the land we have and used the slope the best we can. I look forward to people's thoughts and additional ideas.

None of the suggestions so far, hit your brief which was for a lush tropical vibe. Nearly all the plants suggested are for temperate gardens. To create the tropical vibe it's all about the leaves. Luckily you have the perfect orientation for just such a garden. Here's my pics. Along the top of your retaining wall plant Alocasia, otherwise known as elephant ears. These are essential in a tropical garden as you need big leaves for a lush look. Alocasia come in many varieties and lots of different colours. Choose the one you like best. They grow in part sun, but can tolerate short full sun hours and nothing looks as tropical as these babies. Alocasia do send out runners so if you don't want them spreading up there you can pot them up as pictured. Putting these up high will create a canopy-like feel of big jungle leaves. Next you need smaller leaves and colour, enter an Indonesian tropical plant that is very popular but in your climate will do best with only morning sun. Croton. These are everywhere in QLD and other subtropical gardens. They are slow growing so you never need to trim them and top out under 2 meters high. They have the best colour when planted under taller plants where they receive dappled light for short hours of the day. Too much sun and their leaves bleach. They come in many different varieties, many colours and leaf shapes. They are a beautiful low maintenance plant. Croton do great as a potted plant as well. It's not a tropical garden without a water feature. I favour still water features which are simple to put together. The most expensive part will be the glazed bowl which depending on size can run about $200 but it's a one off investment. One of these with either a water lily (not lotus it's too big) or a papyrus, throw in some frogbit which is a floating water plant and you'll have this.... As long as the bowl is less than 30cm deep you won't need council approval or a pool fence. This particular bowl is growing a sedge (tall grassy stuff) arrowhead (the triangular upright leaves, you can eat the bulbs) a small water lily and a canna. Perfect for a tropical vibe. For something to cascade over the edge I'd avoid the Dichondra silver falls pictured in other answers. They create a dry climate rather than tropical look. Great tropical cascaders include... Syngonium, you can get this at any garden centre or take a drive around local parks it's often growing wild as a garden escapee. It's very easy to strike. Just pull of a section with a bit of root attached and stick it in your ground. Hoya, or wax vine. Few things look as tropical. Also very common in garden centres. Or another option is to grow this native, DIanella silverstreak all along that retaining wall and let is cascade over the edge. It grows full sun to part shade. It's easy to buy in bulk for a mass planting. Once you've got the big stuff planted up, you'll have patches of sun and shade that you should fill with creepers and other low growing plants that take your fancy. Silver Lady ferns are hardy and look great in a shady spot. You cannot go past a birds nest either as they famously take even full sun without burning. This ones growing with caladiums (miniature type of elephant ear in very colourful variations and a grass. While single plant mass plantings look great around hotels and public parks. A backyard is much more interesting if you mix up the plantings with carefully chosen combinations that create height, big leaf drama, colour and texture. Tropical gardens can be very cool. Look at all the different heights, leaf colours and textures here. Creating the tropical look is about creating a canopy effect with some tall plants, big leaves, coloured leaves and creepers. PS - Forget about bamboo. Someone planted 20 clumps of the stuff in my garden, it's ugly and impossible to remove as the rhizomes are like concrete and need a bobcat to dig out. What people don't tell you about clumping bamboo is that the clumps continue to get larger and larger taking over your garden. It also regularly goes through periods of looking awful.

Everyone that visits knows that the support pillar is there for a good reason. As @Kate has said, use it to define the different living areas. You could put a buffet up to it or a big pot with indoor plant.