In 2008, I wrote about how to make a Halloween vacuum cleaner costume, with attachments. I know that Halloween is coming every year when people start to find that post.
Go there to look at it (now; thanks) and then some more ideas:
Read Engelbert Sneem and his Mean Vacuum Machine, a 2007 kids picture book by Daniel Postgate from North-South Books.
@zephyrbunny on Flickr has a photo set to build a Roomba costume.
From Puppet Junction:
For one of her first costume building jobs, Serra Hirsch built a Vacuum Cleaner Costume and portrayed the character of Bertha the Vacuum Cleaner for the Looking Glass Theater's production of I Hate Spinach!