Just an update andrewkm stated it will be up in 3-6 hoours( which was 3 hours ago ) So it is about 0-3 hour ETA.
Ok I'll just explain it. go to your screenshot and open it in paint. Use select and select the area of chat you want. copy that. Do select all and delete everything. Ctrl + v to paste the screenshot back in. Then, drag the white "paper" so that it "hugs" the photo . Save that and upload it to here. Then, click the picture and copy the url. Go to your signature and click the tree photo and paste in the URL. Hope this helps...