I may not be the first to come up with this idea, but here are some photos of my $5.00 way of catching all the stuff that comes off the engine during cleaning.
Not wanting to work out in the driveway or make a huge mess in the garage. I made a quick trip to the local Toys"R"Us store. Just inside the store in the very little kids department, I spotted just what I needed. A 36" round by 6" tall inflatable kids pool. The perfect size to fit between the wheels and still fit under all of the engine. The soft side makes it easy work work around. I might start doing this on every oil change.
In this case, I shot the engine cleaning spray on the car. While giving it 15 minutes to do it's work. I fired up the Ultra Steam Shark II and put on my eye protection. The small steam cleaner allowed me to hit the engine with hot steam and rinse at the same time. The steamer does not use much water, so it took a couple of tank loads to go over the entire engine and other under the hood areas. The steam helped in some of the thicker spots. I then gave it a quick rinse from the hose. All of this only came to about 3 or 4 inches of water in the pool. What you do with the dirty run off is up to you.