Don't worry about not having a flower girl, every wedding is different now. Depending on where your ceremony is, you could possibly have flower cones for your guests to toss after the wedding if you wanted that for part of your pictures.
There's not a real 'formula' anymore. What matters most is that the people that matter to you are closest to you on this important day.
If you have more than one boy that you would like in the ceremony, have a couple of ring bearers. One for each of your rings.
A recent bride had her dog (very highly trained) stand in the ceremony, and was part of everything. Her dog was a member of her family and she would not have it any other way.
Although your wedding is a day to look your best and have beautiful things around you, it's the feelings and the people that matter most. That's what you'll carry with you, that's what you'll remember when you look at your photos.
Make your ceremony your own. My very best wishes for you!