Is it possible to generate a sprite sheet larger than 100 x 100 for my game I would like to use this tool for making a snowy background but I'd really like a higher resolution to export to so the repeating tiles are less obvious. 

Ok So I figured this out by my self under the custom  tab you can change the canvas height and canvas width to way above their intended maxima If you do 1600 by 1600 and have a scale of 4 you'll keep the pixilsation effect this tool gives you and produce something at 400 x 400 just remember you'll need to adjust the width and height of the emitter accordingly and the life as well under the particles tab.  And you may also want to change the number of particles being produced.  Also this comes with a huge disclaimer my computer squealed quite a lot whilst doing this and had some major slow down. But the results were very worth it.