Yes!! I do it all the time! Well, not before I buy fabric :oops: , but certainly before I cut it.
I use the fabrics I no longer like, those I never liked, those that have misprints, any of the 'uncool' stuff that seems like it will never get used. Being chosen for a sample block gives them a 'reason for being'. They sacrifice themselves to become a test case for a new block, a new technique, a new frontier! It has saved me a great deal of time, fabric. frustration and boredom over the years. :-D Can't say I would ever want to put all those blocks together in anything though.