Sources, left to right and top to bottom, as far back as I've succeeded in tracing them:
1. Modified from http://lh3.googleusercontent.com/BvtTarYSTB2IZS93wJeXwAa53c-wUsGFgWTMTz0sPhv8soSNN-EHLx3wEvTB63Vp8dviZwRP=w176-h220-p-no; the originator *may* be one Deebu P. Solomon, although their Peperoncity account is now defunct: http://f1.pepst.com/c/29CCD4/332473/ssc3/home/062/deebu.p.solomon/albums/minnal.gif_480_480_0_64000_0_1_0.gif
2.Modified from http://lh5.googleusercontent.com/-2uPehSvtRUA/TWksCJQrj2I/AAAAAAAAAl4/6toOAJlo0y4/s1600/Chuva2+gif.gif on a post at http://jogosts.blogspot.com/2011/02/wallpapers-gifs.html; the earliest version I've found so far (June 12, 2010) was uploaded by stissa88 at http://www.ownskin.com/gif_detail?t=c6UFYWU7
3. Here's one whose exact originator I've been able to trace: modified from https://imgur.com/tA78xWb by @fugulolo: http://www.reddit.com/r/gifs/comments/1pp01a/rain/?st=jeho0u80&sh=76760203
4. Modified from http://oi47.tinypic.com/2nropyh.jpg, now defunct.
5. Modified from https://lh3.googleusercontent.com/0ZaV5-iCFhOuu0AJfr5AgjTupTccSUI9IMEITfvWXNAemZcYyQlJK6pdSPe0WPD1WaFp3FCCLBplrFI=w289-h220; the earliest version I've found seems to be by Bia Tomaz.
6. Modified from http://files.fatakat.com/2010/5/1272891685.gif.
7. Further color modification of the source of # 2.
8. Taken from http://f0.yomowo.org/c/298B07/224905/ssc3/home/015/clo176x220/albums/rain190210_1.gif_480_480_0_64000_0_1_0.gif, and appearing earlier at http://www.umnet.com/pic/diy/screensaver/1/Rain-19813.gif; both are now defunct. A current link is at http://i.imgur.com/Xia8y8C.gif .
9. Modified from http://www.animated-gifs.eu/category_nature/phone-240x320-rain/0118.gif.