Patterning centers are the easiest to make and can fit into every theme. I've gotten a lot of rubber manipulatives by themes through scholastic book clubs. They were about $10 each set. They are well worth the money. I have seen apples, Halloween, fall, back to school, bugs, transportation, Christmas and others.
I have used holiday stickers to make simple pattern cards. Children can copy and extend the pattern I've made.
Unifix cubes are easy to make color patterns. I have made cards on sentence strips for children to copy. I also use the colors we are working on. Put two colors like orange and black for Halloween in a basket and set it on the table. Children can't help but find the pattern. While roaming the internet I did find a printable sheet of unifix cube patterns, but I will have to find it again to share it with you.
Pattern blocks have many shapes that can be made into patterns. Here is a colored or black and white printable using pattern blocks.
You can make patterns with anything.