Symbols made using simple shapes

It's not always easy to explain concepts using words alone, so sometimes it's best to use a picture to illustrate it. Of course, sometimes people want to incorporate references to these concepts in architecture or other designs, and words aren't going to be useful for this. As a result, over the centuries many concepts have been tied to simple geometric designs.

Since pictures can be made up of many different elements, they can also build on existing meanings by merging symbols or by adding things to existing designs.

The rest of this page provides an overview of many common shapes and designs used to represent something in Christianity and some information about them. If the name of the symbol is a link, click it for a tutorial on how to draw the symbol.

Stars

4 Pointed Star
When you think of Christian stars, this design and the similar Nativity Star are probably the first designs to come to mind. Made from just four points, this star forms a simple cross. It represents the famous star that announced the birth of Jesus, and so you'll normally find this design above a manger.
7 Pointed Star
The meaning behind this design is less of a representation and more of a way of reminding us of something important. Just as there are seven points, there are seven Gifts of the Holy Spirit.

These important Gifts are Wisdom, Understanding, Right Judgement, Courage, Knowledge, Reverence, and a proper Fear of the Lord.
8 Pointed Star
Also known as the Baptism Star, this stretched out design represents the regeneration of mankind through baptism.
10 Pointed Star
Each point on this star represents an Apostle that neither betrayed nor denied Christ. Even though Peter was quickly restored to a good standing before the Lord, being lumped together with Judas Iscariot is probably one of the least flattering ways he's referenced in symbolism.
Creator's Star
Also known as the Star of Creation, this symbol emphasizes the Trinity's role in creation by representing it twice (see the Triangle, below). Additionally, the six points on the star are said to bring to mind the six days it took for God to create the world.
Epiphany Star
A radiant star in a circle like this represents the Epiphany; that is, it represents the birth or manifestation of Jesus Christ. Thus it's often seen as part of a Nativity scene.

Since this is a pentacle, Christians aren't going to be quick to use it in art today. Many Christians see pentacles as evil or satanic, after all. More realistically, while some pentacles really are used in Satan worship, the majority of pentacles are used in peaceful druidic religions.
Nativity Star
This is a variant of the 4 pointed star. Like the original design, it's used to depict the star that led the Magi to Bethlehem.
Star of David
The Star of David is a very well known symbol for the Jewish people, their faith and their nation, so this design was probably not something you'd have expected to see in a gallery of Christian symbols. However, this is sometimes used as an alternate design of the Creator's Star.

That said, to avoid confusion it would probably be better to use the other design or find a different way of expressing the idea altogether.

Generic Shapes

Circle
Circles are basically lines that neither begin nor end, so it's fitting that they are used to represent eternity or things that are eternal. One example would be God the Father.
Square
While circles are used to represent eternity, squares are used to reference earthly things. One example is the Square Halo that is sometimes used to denote a living person.
Triangle
A simple equilateral triangle like this can represent the Trinity. It can also aid in the explaining the nature of the Trinity. A triangle in only one shape, but it has three distinct points, much like how the Trinity is one Being but three distinct Persons.
Triangle with Circle
Combining a triangle with a circle merges their meanings: it represents the fact that the Trinity is eternal.

Other Shapes

Fleur De Lis
While it's more commonly known as a symbol for French royalty, the fleur de lis is also a popular symbol for the Virgin Mary.
Quatrefoil
Four interlocked circles typically represent things that come in groups of four. The usual examples are the Four Evangelists or the Four Gospels.

You'll frequently see this design in church windows or archways.
Trefoil
Three circles intertwined has been a religious or magical symbol for quite a long time. In the context of Christianity, it refers to the Trinity itself and the fact that all three parts are eternal.
Trefoil (alternate)
An alternate design for the Trefoil, this variantion leaves out the central portion. This is just a decorative change, as the meaning remains the same.
Triquetra
This interesting shape is sometimes used to represent the Trinity, as it forms one shape using three arcs. Note however that pagan cultures also used this design, so it seems to have been appropriated from other religions rather than created for Christianity.
Triquetra and Circle
Adding symbols together merges their meanings, so by adding a circle to the standard triquetra we've added a reminder of the Trinity's eternal nature. Unlike the regular triquetra, this design seems to be unique to Christianity.