There is much debate on whether a warm-up activity should be related only to previous lessons or to help introduce the day's material, or whether a warm-up can be totally unrelated to the students' curriculum. I am of the mind that if you don't have your students engaged and ready to learn, you can't teach the curriculum anyway, so I always liked to do warm ups I thought my kids would like. The choice is yours. Either way, the idea is not to take up too much of the class time, but to get students' brains moving, focused, and ready to learn!
Have you ever considered a Word of the Day program? I used a Word of the Day (WOD) for several years to help my students (A) focus at the beginning of class (as we completed the WOD during the first 5 minutes), B) improve their vocabulary, and C) grow their decoding skills by learning the meaning of hundreds of affixes and root word meanings.