One of the things I do when I need to find the right pattern, or fabric, or quilting motif is to lay out the offending pieces in a conspicuous place where i see it all the time, in different lights of the day. I walk past it several times a day - can't miss it.
You never know where or when inspiration can strike.
Most of my quilts are my own design, or modified designs. Most of my "designed" quilts started with just a basic idea and "morphed" into what they became. I have yet to design the complete quilt on paper - and make it exactly as designed. Something always happens and I get a different idea at some point down the road and ~poof~ the design has changed.
A possible solution for your current block dilemma ... how about making the block you wanted to make but make them BIG blocks to highlight the rocket ships. Perhaps 3 BIG blocks set in a single vertical row. Border those with small blocks using the same fabrics (except the rocket ships). Small plain border in a solid color, then a large border of the rocket ships to pull it from the 3 big center blocks. Will that work??