Download the haven res tool, the second link here.
viewtopic.php?f=27&t=5853#p66606Download the haven-res.jar, the first link here.
viewtopic.php?f=27&t=30126Put them both in one folder. If you have 7-Zip, right click haven-res.jar, go into the 7-zip menu, click "extract here". If you don't have 7-Zip, get it.
Tip: If you want to keep all the client mods you already have, after the 7-zip extraction is done, copy paste the res folder from your ender's client, into the folder with the haven res tool and haven-res.jar. Replace all the files
Double click the haven res tool, the window should be "extract", click ok. A bunch of junk will pop up, wait until it says finished. It might take a while.
Then go into the out folder, and track down the image you want. It can take some time to know what the folders contain, and make the changes. Only mess with the .png files, don't touch the image layer or metadata.
When you're done, go back to the main folder, double click haven res tool, go into the drop down menu, and select encode. Copy paste the specific file path of the image changes.