Since the tiger lily bulbils are dropping and "planting" themselves naturally around the parent plant now, you can keep them for a few weeks in your garage before they start to slightly shrivel. They'll start pushing out a little root almost immediately. DO NOT REFRIGERATE.

You could also just spread them out in a shallow tray with ordinary potting soil - keep in your garage or protected spot until you're ready to put them in their permanent place in the garden. When you put them in their permanent spot, be sure to mark the place - next year they'll look like a shiney blade of grass and are easy to step on or pull up when weeding, etc. Make sure you don't bury them deep; they pull themselves down by their root action to exactly where they want to be. It'll take at least three seasons for them to reach blooming size.