Here are some Tau ideas from my own collection.
The rectangular tanks are 1 litre yoghurt pots stuck on to mouse mat holders that were being thrown away at work.
The silos in the middle are Marks & Spencer prawn dim sum packagings.
The leaf shaped tower in the left foreground is a shampoo container.
The domes are a Japanese plastic miso soup bowl. I got a dozen of them in a sale for about £1 each.
The soup bowls are blinged up with tops off various spray cans, and detail parts from Antenociti's Workshop.
The oval tank in the middle is the lid from a pump dispenser soap bottle, mounted on a CD. Poster made by me using ink jet printed transfer paper.
Loads of cheap or free household items can be converted into futuristic Tau terrain with the help of a few detailing parts, plastic card, and some spray paint. I use a textured spray that gives a variable colour and a rough surface in the same spray.
The toileteries section of your local supermarket is a great place to find weird shaped bottles that can make alien towers and fuel tanks.