I'm the one who created the sig!
wink 
I gave as much info as I could about each symbol. If you want more info on any particular symbol, let me know.
In the order they appear above:
(first row)
1- Baha'i
2- Confucianism (This symbol is the Shuang Xi, or double happiness, and is common throughout China.)
3- Christianity (This symbol is the Ichthus. It was used as a Christian symbol in the early church before later being replaced by the cross. It is making a comeback again today. Some Christian denomiations do not use the cross as a holy symbol, but DO use the Ichthus.)
4- Hinduism (This symbol is the written form of the mantra "Om".)
5- Islam
6- Buddhism
7- Neo-Paganism (This symbol is known as the triple goddess, representing youth, the prime of life, and old age, all reflected in the phases of the moon.)
8- Satanism (Specifically, this is the symbol of the Church of Satan, but it has been adopted by Satanists outside of that particular group as well. It represents the goat of the sabbat and mankind's power over the four elements.)
(second row)
9- Shinto
10- Sikhism (This symbol is the Khanda. It is made up of three different traditional Sikh weapons, and represents unity, truth, justice, and spiritual power, all through God.)
11- Taoism (Yin Yang. This symbol represents the balance of opposites in the universe.)
12- Wicca (While often used by non-Wiccan Pagans, the pentagram is most commonly used by Wiccans. It represents earth, wind, fire, water, and spirit, spirit being the top point of the star.)
13- Jainism
14- Universism
15- Christianity (The cross symbol was first adopted by the Catholic Church in the early middle ages and has since become the most widespread symbol of Christianity in the world.)
16- Judaism (The star of David)