How to create tilted (height) isometric tiles

This is perhaps best explained pictorially. I am trying to create a 2.5D isometric game. My vision is for the game to look something like my goal:

I am not a graphics artist, so I'm having some trouble creating the "tilted" tiles to simulate terrain of different height. Creating the basic isometric tile was easy using the following steps:

1. Create a 64x64 square version of the tile



2. Rotate by 45 degrees


3. Scale the height down by a factor of 2

Creating the "tilted" tiles is more of a challenge. At my disposal I have Photoshop, but I am far from an expert at using it. Here is my current problem:

I am not sure how I can manipulate vertices, otherwise this would be easy, but basically, to get a "tilted" tile from my basic isometric tile, all I need to do is to shift the bottom and the right vertex down by 16 pixels, while fixing the other two vertices. This would generate the tile I want.

What is an easy way to accomplish this. Is Photoshop the right tool for this? Any suggestions?