The best advice I can give when you are looking to make your own invitations is to keep it fairly simple, as you will need to duplicate the design lots of times. Have a look at what the professional wedding stationers are producing to get ideas.
A great way to copy your wedding invitation is to design the invitation on your computer and then print it out. It is worth checking with local printers the cost of this as this may be cheaper than printing them all at home. Cartridge costs can soon add up!
Another duplication process is to use rubber stamps, there are loads of great designs that you can either get from a local craft shop or online.
You could keep the invite very simple and buy a wedding invitation kit, this will give you everything that you need to put your cards together and then all you will need to do is personalise them.
Ribbons are a simple but effective decoration, just think about the amount of bows you will need to tye! And get help in for a mamouth bow tying session.
For some light hearted inspiration on wedding invitations have a look at the following clip, it had me in stiches, enjoy!