As a legal document, the ketubah dates from at least the time of the Babylonian exile, about 2000 years ago. It outlines the financial obligations of the groom toward the bride and protects the bride in the case of a divorce. All Jewish marriages require that a ketubah - one that uses a text that is recognized by either the Conservative or Orthodox movements - be witnessed, or signed, by two people. Depending on your rabbi, it may or may not be OK to sign just the custom designed ketubah (even if it does use a traditional text). Most rabbis will have a preprinted ketubah which they will prefer your witnesses sign. That's OK, you can have both ketubot signed.

So, if the rabbi is going to give you one for free, why have a one designed for you? One reason has ancient roots. Like all Jewish ritual objects, a hand-crafted ketubah fulfills an old tradition, called hiddur mitzvah, of using the best, most beautiful objects to intensify, or glorify the fulfillment of the mitzvah (commandment).

You can take advantage of this tradition to make your ketubah more meaningful to you.
Over the years
the ketubah has come to be much more than a legal document. It's a symbol of your love for, and commitment to each other. As such, it's fitting that it reflect something of your taste. Two ways of doing this you can do this two ways:

Customize the design
Since the ketubah is a legal and not a religious document, its design isn't affected by religious restrictions: it can be written by anyone, with anything, on anything, in any style. more...

Customize the text
If you want to stay with a traditional text, most rabbis will allow you to include an additional text in another language.