I loved the Toy Tool collection this is remixed off of but wanted more plates. I tested all these with the 6x1 plate from the originals. They all fit will. 

• The 5 holed circle plate is very similar to the original but I felt it fits a small amount better.
• The slotted plates are for connecting on angles that might otherwise not line up
• The 1x1 is a good spacer if you're stacking a lot of pieces
• Hex Circle plate allows connecting off center.

I also uploaded the FreeCad file, in case anyone wants to make more. I'm very beginner on my CAD skills so it may not be the best. If you have ideas for other shapes I'm happy to try to make them.