What is it though? Any floor plans?

for what kind of space

Decoration idea for what space??

You have mention the size, by that I hope you are asking for Pooja area decoration idea?

Thanx for your valuable reply,, I am asking about this space.. it's not for Pooja space but any other idea like fountain type or anything else!!!!

A space of 3×4×12,   12 feet is height,3 Breadth and 4 feet is depth... any decoration idea please???

Depends on where is this space located,is it in a house? If it's near a window and receives bright light, consider adding a tall indoor plant, and with a small table next to it which can hold a meditating Buddha idol and some candue holders.

Or you may hang a single jhula and decorate that space with some fairy lights. But really depends where it is located