I am also thinking, some Orchids like Dendrobium aggregatum prefer to grow mounted and do get to be sizable plant also.
We really need to see the original poster to please chime back in here. I could imagine plants being watered over trays, sitting on a rack of sorts. One can go on and on.....
Beautiful small plants quite suitable for windowsill growing are Neofinetia falcata, these are miniature gems which are very pretty to look at, even when not in bloom. They bloom in the Spring and the delicate and beautiful blooms are very fragrant in the evening. One might want to google them... The downside is that they can be expensive, it helps to shop around a bit.
