Look for Patterns – Some of the boards are mirror images of itself. So if you solve one side of the board, the other side is easy. Be on the lookout for subtle variations though, sometimes each side will have slight changes in the pattern.
Take a Screenshot – Each board only allows a set number of mistake, once you reach that number, you will have the start the board all over again. If you are down to your last mistake, you may want to take a screenshot of the board that you can refer back to if you have to start again.
Dig Holes – If you are stuck, try digging holes around the tiles you know are correct. You can either switch between the shovel and the brush tools on the lower right side or you can right click to use the shovel.
Start with the Edges and Larger Numbers – Getting started is the hardest part of each board. Look for the larger numbers and work on those first. Also, try to solve the corners and the edges of the board and work your way towards the middle.
These are just a few suggestions that will help with World Mosaics. If you have any general tips to share, please post them here