Besides making the bag bigger, I also decided to add some pockets to the inside to hold diapers, bottles, pacifiers etc...
First of all I made a hanging pocket much like the original wasp bag suggests, just bigger. Here is how I made mine:
I cut three pieces of fabric from my red lining.
1 - 9 in x 8 in
1 - 9 in x 6 in
1 - 9 in x 3 in
Then I sewed the zipper into the two smaller pieces.
Put right sides together and sew around the bottom three sides at 1/2 inch seam allowance. I then used pinking shears to finish the edges.
Turn your pocket right side out and press.
The other change I made to the inside of the bag was that I added a row of elastic pockets to one side of the bag.
To do this I first cut an extra piece of lining fabric that was the same width as the panel on the bottom, but I angled the edges out to be about 2.5 inches wider on each side. The height of the pocket is up to you, but I made mine about 10 inches tall.
Here is a picture showing the original lining panel folded on center front on top of the pocket piece. As you can see the pocket wings out at the top to allow room for things to be put inside the pockets.
Now take your pocket piece and sew a hem that will act as a casing for your elastic on the top of the pocket piece. To do this I first folded the top over by 1/4" and then by 3/4". I sewed close to the edge to allow enough room for my 1/2inch wide elastic.
Insert your elastic using a safety pin. Cut elastic to desired tautness and secure by tacking both ends with your sewing machine. I made my elastic 2 inches shorter than the bags width. This way it was tight enough not to allow things to fall out.
Lastly, sew at 3/8" seam allowance with the wrong side of the pocket to the right side of the lining. It should look something like this:
At this point you may want to sew vertical lines to divide the pockets up into smaller sections which I ended up doing later on.
This is the end of changes I made to the wasp bag to make it diaper bag friendly. Check back to see my finished diaper bag.