First off, just want to give credit where it's due by thanking Terah Valeth for creating the health meter in photoshop.
I was getting rather annoyed at eye balling an enemy’s health bar to guess around what percent they're currently at, mostly to know when Garuda is going to perform her astral flow, but for other reasons as well. I decided to look into image dat editing, but found out it's impossible to edit the health bar to show percentages of the enemies health (the health bar is made up of 3 images, one of which is only a pixel or two wide, which is the part that allows you to stretch the health bar).
So I decided to use an image viewing program that didn't have any visible interface and can display transparent images (.PNGs), then change the properties to always display on top, then move it over top of the health bar in-game. I found a rather neat program called Impression Eyes that can do just that.
Here’s a screenshot in-game of what the health bar looks like. (Click image to enlarge)

Compass Overlays
I also made a compass overlay, So far I've made a basic version and a modern version, but I'm working on a couple others. Here's a screenshot of what they look like, you can download them at the bottom of this post.
Modern Styled Compass

Basic Styled Compass

Impression Eyes
Impression Eyes is an image viewer without any visible interface, so you can view/display JUST the image and nothing else. All functions can be performed by right-clicking the image or through keyboard shortcuts, there are quite a few neat features, you should play around with some of them and get more familiar with the program.
Setting up Impression Eyes
Impression Eyes is a free program to use,
here's the download link: http://www.utilhaven.com/file/ImeSetup.exe
After you download/install the program, run the .exe, you'll see a black box with the words 'Impression Eyes' in the center

Drag and drop an image inside the black box (for example, the custom health meter), and it will instantly display that image. (You can download my custom health meter further down in this post)
It should look like this, to get rid of the black background, press F7

F7 will toggle transparent mode, which you'll need for the custom health meters
F8 will toggle always on top, which you'll also need for the health meter so it stays visible when playing FFXIV.

Indicating Low and Critical Health
In the game, if your health or a party member's health drops below 50%, the numbers turn to yellow to indicate low health. If they drop below 25%, they turn red to indicate critical health.

The custom health meter's frame and numbers has a yellow accent from 50-25% to indicate low health,

and and has a red accent from 25-0% to indicate critical health.

Different Sizes and Downloads
My brother (Terah Valeth) created the custom health meter in photoshop, I then took that and made a few minor tweaks and created a total of 5 different sizes to better suit personal preference and different resolutions.
You'll notice that the health meter doesn't display a number for 10%, this is so it doesn't cover/interfear with buffs & debuffs on characters and enemies. Also, there are very slight lines to indicate each single percent (it's hard to see in the screenshots, but it's more visible in-game).
Size - Very small (Width: 563 pixels)
Download Link: http://www.mystina.ffxivmaps.com/Heath%20Meter%20Screenshots%20&%20PNGs/Health%20Meter%20-%20Very%20Small.png

Size - small (Width: 663 pixels)
Download Link: http://www.mystina.ffxivmaps.com/Heath%20Meter%20Screenshots%20&%20PNGs/Health%20Meter%20-%20Small.png

Size - Medium (Width: 763 pixels)
Download Link: http://www.mystina.ffxivmaps.com/Heath%20Meter%20Screenshots%20&%20PNGs/Health%20Meter%20-%20Medium.png

Size - Large (Width: 863 pixels)
Download Link: http://www.mystina.ffxivmaps.com/Heath%20Meter%20Screenshots%20&%20PNGs/Health%20Meter%20-%20Large.png

Size - Very Large (Width: 963 pixels)
Download Link: http://www.mystina.ffxivmaps.com/Heath%20Meter%20Screenshots%20&%20PNGs/Health%20Meter%20-%20Very%20Large.png

Red Tick Mark
I created a small tick mark, you can move it around and place it anywhere on the health bar. I used it to indicate right before Garuda goes below 60% health, but you could use it for other things such as Ifrit or whatever.
Heres what it looks like in-game
Download Link: http://www.mystina.ffxivmaps.com/Heath%20Meter%20Screenshots%20&%20PNGs/Health%20Meter%20-%20Flag.png

Compass Overlays
I've made a couple different compass overlays (modern and basic style), and I'm working on a few other aswell. Use Impression Eyes to display the compass the same way you did with the health meter, then align the 'N' on the compass image with the 'N' in-game. Enjoy ^^
Modern Styled Compass
Download Link: http://www.mystina.ffxivmaps.com/Heath%20Meter%20Screenshots%20&%20PNGs/Compass%20-%20Modern.png

Basic Styled Compass
Download Link: http://www.mystina.ffxivmaps.com/Heath%20Meter%20Screenshots%20&%20PNGs/Compass%20-%20Basic.png

.PSD Files
Here's the .PSD files for anyone who wants to use the health meter and/or compass and make edits to them.
Just please give credit to Mystina Valeth & Terah Valeth if you post them ^^
Health Meter:
http://www.mystina.ffxivmaps.com/Heath%20Meter%20Screenshots%20&%20PNGs/Heath%20Meter.psd
Compass:
http://www.mystina.ffxivmaps.com/Heath%20Meter%20Screenshots%20&%20PNGs/Compass%20Overlay.psd
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pro doesn't let me use a signature? cool story, bro.
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