There is currently no maximum number of images you can upload, although you are limited to the number you can upload at a time (Premium members can upload 100 at a time).
With grids, there are limits. In our web-based version you’re currently limited to a 6×6 grid. With our program version for Windows and Mac, you can start with a 10×10 grid and then insert images into the grid by dragging them between 2 cells, however this would be a tedious way to create such a massive grid.
Let us know if you have further questions.