PicArtia is not completely free, only mid-resolution photo mosaics are free, if you want to create a high resolution photo mosaic you need to pay. But if you just want to have fun with photo mosaics and want to test photo mosaics this tool is for you.
Currently it only supports image upload from your hard disk or any internet photo, but in future you will be able to create photo mosaics by pulling photos from Flickr likes.
To create photo mosaic click the start button on PicArtia home page and upload a photo from your hard drive or point an image from the internet. The second step is to select an image from the gallery, once you select an image from the gallery go to the third step to generate your photo mosaic. You need to enter your name and Email here, you will receive your mosaic details via Email. It takes time depending on the size of your output file. Go and create your photo mosaics and have fun.