Sculptures made from tights stretched across a variety of structures.  Similar with giant condoms. 

Giant bags in framework collecting water from dripping pipes.  Giant coloured balloons continously inflating and deflating.  Stretched membranes which collect detritus.  Netting collecting wind blown debris.  Make collectors from sticks and similar natural materials.

Pits in the ground which accumulate rubbish.

Floor composed of squirming mass of invertebrates.
Fungus or lichen covered wall - made to grow in distinct patterns.
Bacteria in petri dish.

Colour clouds with dye, paint on them, project imagery on them, infiltrate them with coloured gases or make them produce coloured rain.  Cut clouds into sections; join them together; distort, extend or contract them.

Build a theatre on top of a cloud, build an art gallery on or in a cloud.

Make clouds in the gallery, make fog, wind, rain or an unbearably hot sun.

Coloured lakes and coloured rivers.

Bounce sounds off all aspects of the landscape: permanent and ephemeral.

Coloured clouds float over coloured rocks.

Ranging from single person igloos to large family versions.  Some versions could be mobile or even motorised.

Multi-storey igloos, underground igloos.  Igloos with built in heating, refrigerators and televisions.  Build a giant igloo at Crystal palace.

Blow up igloos, build your own igloos with plastic bricks, organic igloos and nano igloos.

Underwater igloos with completely transparent walls, overground igloos with fish tanks built into the walls, flying igloos built with lighter than air bricks or igloos with hot bricks that slowly sink into the ice.

He wants to make sculpture out of this material: sculpted (in various ways) or just thrown - even dropped or deposited randomly in other ways.

Sculptures or paintings set in farmyard manure.  Speakers set in farmyard manure from which poetry is recited.  A complete rendition of "Animal Farm" from speakers hidden in fresh farmyard manure.

Farmyard manure spray painted or with small plastic animals embedded in it.  Farmyard manure with fragrant flowers strewn across it.

A grave in farmyard manure.  Animal bones in farmyard manure.  A model city built on a mountain of farmyard manure.  An obelisk of farmyard manure filmed over a period of time - finally set on fire.

A nice crop of vegetables growing in a pile of old farmyard manure.

There could also be radio attachments, umbrellas or even a remotely controlled hand - or JCB bucket (for small jobs in the garden).  Microphone and loudspeaker for intimate communication.

Another possibility would be brightly coloured sculptures or giant items of jewellery.

A scalemodel spitfire or replica ship is another potentially interesting possibility.

Torch attachment or burning/smoking material.  Draw with light.

Water pistol.  Small calibre hand gun (penis gun).

Motorised penis attachment for inveterate flashers.

Sculpture to be attached to top of hat.  Spinning sculpture for hand.

Motorised painting fitted into breast pocket which rises up by voice activation.  Version for back pocket which also flashes light when person turns corners.

Stereo painting across bra.  Low relief sculpture on thin metal underpants.

TV screen across T Shirt or revolving on top hat.  Suit made from LCD screen.

Clothes that change colour according to orchestrated programming.  Automated version which change colour according to temperature, air pressure or emotions of wearer.

Painting for bottom of shoe.  Sculpture for top of shoe.

Micro sculpture for navel that shoots out like cuckoo from clock.

There could be bridges combined with sculptures or bridges leading to/connected to paintings.  Also, Half Bridges that appear from wall or  are attached to items of furniture.  A bridge that connects to a painting of a bridge.  Small bridges that are assembled in series on boards.

Clothes bridges that can be worn or pulled on behind on wheels.

The bridges could be over or under water; through fire or smoke or have impassable obstacles in the middle.

Bridges between art and life.

A fountain emerges from the centre of a horizontal painting; a waterfall issues from a vertical one. 

A horizontal painting underwater in a stream or tank with artificial waves.  A sculpture in a sand storm.

A  floor painting with a water frame, painting with transparent frame filled with swirling gas, painting with fire frame or painting with rock formation frame.

Sculpture partially buried with pile of earth, manure, leaves, seaweed or coloured sand.

Transparent sculpture with fish inside, cage sculpture with birds inside or giant sculpture with people inside

A horizontal painting used as a table with food covering it, folded painting to be used as a chair or a vertical painting with clothes hanging from it.

A painting with a large  hole drilled in the middle so it can fit over a lavatory seat, a painting hung so that darts can be thrown at it or picture angled to provide an archery target.

A painting to fit in a cat litter tray, painting to fit in the bottom of a bird cage (with light covering of sand) or a small paintings to be dropped in a fish tank.

Painting to be used as a bread board, painting to be used as door mat or painting (with non slip surface) to sit in a bath.

Paintings, in various sizes, to be used to fill holes in fences.

A mural to stand behind a soccer goal, triptych painting to act as cricket stumps or painting as a diving board.

Painting on box designed to fit over a television at the end of the day.