Hi! If you search the business forums, there are a lot of threads about the importance of titles - particularly the first three words used. Relevant titles help you to show up in more searches and get more sales. So using "Buy 2 Get 1 Free" won't help to increase your relevancy in scrap booking searches. I would definitely go with the second option you have listed - Digital Scrapbooking: Color or Theme (Spring, Owls).
Then again, you are doing amazing with sales so maybe keep doing what you're doing. I would check your Shop Stats and monitor to see if items with "Buy 2 Get 1 Free" are clicked on more!