Now you can also social media icon instead of any image .Just feel free to add image signature in gmail .
These are the some social media icons :
Social Site Name
Icon
Image URL for use in Email Signatures
Blogger
https://www.frip.in/wp-content/uploads/2010/11/blogger.png
Delicious
https://www.frip.in/wp-content/uploads/2010/11/delicious.png
Digg
https://www.frip.in/wp-content/uploads/2010/11/digg.png
Facebook
https://www.frip.in/wp-content/uploads/2010/07/facebook.png
Flickr
https://www.frip.in/wp-content/uploads/2010/11/flickr.png
FriendFeed
https://www.frip.in/wp-content/uploads/2010/11/friendfeed.png
Google Calendar
https://www.frip.in/wp-content/uploads/2010/11/googlecalendar.png
Google Reader
https://www.frip.in/wp-content/uploads/2010/11/googlereader.png
Last.fm
https://www.frip.in/wp-content/uploads/2010/11/lastfm.png
LinkedIn
https://www.frip.in/wp-content/uploads/2010/11/linkedin.png
LiveJournal
https://www.frip.in/wp-content/uploads/2010/11/livejournal.png
My Yahoo!
https://www.frip.in/wp-content/uploads/2010/11/myahoo.png
MySpace
https://www.frip.in/wp-content/uploads/2010/11/myspace.png
Reddit
https://www.frip.in/wp-content/uploads/2010/11/reddit.png
Blog / RSS
https://www.frip.in/wp-content/uploads/2010/11/rss.gif
Slideshare
https://www.frip.in/wp-content/uploads/2010/11/slideshare.png
StumbleUpon
https://www.frip.in/wp-content/uploads/2010/11/stumbleupon.png
Tumblr
https://www.frip.in/wp-content/uploads/2010/11/tumblr.png
Twitter
https://www.frip.in/wp-content/uploads/2010/11/twitter.png
YouTube
https://www.frip.in/wp-content/uploads/2010/11/youtube.png
All the above social icons are in the standard 16×16 PNG format that are supported by all email clients.
Social Site Name
Icon
Image URL for use in Email Signatures
Blogger
http://img.labnol.org/files/g/blogger.png
Delicious
http://img.labnol.org/files/g/delicious.png
Digg
http://img.labnol.org/files/g/digg.png
Facebook
http://img.labnol.org/files/g/facebook.png
Flickr
http://img.labnol.org/files/g/flickr.png
FriendFeed
http://img.labnol.org/files/g/friendfeed.png
Google Calendar
http://img.labnol.org/files/g/googlecalendar.png
Google Reader
http://img.labnol.org/files/g/googlereader.png
Last.fm
http://img.labnol.org/files/g/lastfm.png
LinkedIn
http://img.labnol.org/files/g/linkedin.png
LiveJournal
http://img.labnol.org/files/g/livejournal.png
My Yahoo!
http://img.labnol.org/files/g/myahoo.png
MySpace
http://img.labnol.org/files/g/myspace.png
Reddit
http://img.labnol.org/files/g/reddit.png
Blog / RSS
http://img.labnol.org/files/g/rss.gif
Slideshare
http://img.labnol.org/files/g/slideshare.png
StumbleUpon
http://img.labnol.org/files/g/stumbleupon.png
Tumblr
http://img.labnol.org/files/g/tumblr.png
Twitter
http://img.labnol.org/files/g/twitter.png
YouTube
http://img.labnol.org/files/g/youtube.png