While messing in iOS settings on an iPad, under General>Accessibility, there's a mode to invert the colors for the screen. If you turn that on and use the app, it looks a bit like the dark theme. Thought I would throw that out there. ^^

I found that Out a Few weeks ago and use it quite often. Another tip: you can set the invertation of colors to the tripple-homebutton-Click. I switch easily that Way.

Hoho, that's great! Easy way to stop being blinded when reading white web pages in bed.

If your iPad is jailbroken and you're willing to put in the money for it you can force the iPad to display a compatible iPhone version, allowing you to use the dark theme.

You need "iFile" and "Retina iPad"

In iFile, open the Skritter app (it's under applications, and then has a long code name), then open the file "info.plist" Towards the bottom there's two lines that read
"(integer)1(/integer)"
"(integer)2(/integer)"

Change the "2" to a "3" or delete the entire line if you like. "2" is the code for iPad compatibility, so if you respring your device it will assume Skritter cannot run as an iPad device and will then display the iPhone version.

Retina iPad forces higher-resolution (2x) images for iPhone software on iPads, but in this case it forces all textures for the program to be used from the iPhone version. If you don't also have this program, Skritter doesn't format the screen properly and you end up with an unusable program.

If you don't like the layout you can always either add back in the "2" line of code in info.plist or reinstall Skritter.