CyanogenMod released a guide (you'll have to join the CyanogenMod Theme Engine Alpha community to follow this link) on Tuesday for the themers among you to submit your themes to be included in the upcoming Theme Showcase (aka Theme Store). This applies to icon pack/launcher theme designers as well as system theme designers. Items you can submit include the aforementioned system themes (now called "Styles") and icon packs, wallpapers, boot animations, font packs, sound packs (ringtones, notification tones and alarm tones) and font packs.

Cyanogen Inc. Community Specialist Brian Resnik provided the guidelines in his Google+ post (again, you'll have to join the CyanogenMod Theme Engine Alpha community to follow this link). You can also find a set of Adobe Illustrator templates and a PDF guide in a zip file there:

What you need to submit:
- Theme APK
- Overview image
- Detail image(s)
- Theme info

Overview Images:
Most important is the image that will appear in the showcase "Browse" list. There are strict rules about what can be in your overview image. Please see the attached "Theme Listing Outline" PDF for instructions.

Additionally, there should be separate overview images for each browsing category (e.g. Icons, Style, etc) that show only that particular feature. Some categories do not require overview images. See the guideline PDF for more details

Templates have been provided in Adobe Illustrator format for creating these images.

Detail Images:
These are screenshots of your theme content. Each image should show unique content for your theme content. See the PDF for further instructions.

Theme info:
Title - Your theme's name
Author - Your name
Package Name - Your package's namespace on the Play Store (e.g. com.flux.theme.flux)
Store Price - Cost on Play Store (if free, leave blank)
Version - Version string (e.g. "1.5.2")
versionCode - Current version code for Play Store listing (e.g. "25")
Description - A one to three sentence description of your theme. (e.g. "GreatFreedom is a theme that is stylishly designed with solid colors, I tried to keep it as close to stock CM as possible apart from the icons.")
Tags - Metatags for your theme (e.g. "60+ icons, Blacked out")
Features - A list of CM-engine features your theme supports. Valid features are: STYLE, WALLPAPER, LOCKSCREEN, FONTS, ICONS, BOOTANIMATION, SOUNDS

For now, you can submit all of the above to [email protected]
Please include "Theme Showcase Application" in the subject line of your email.
In the future we hope to have a web-based submission form
carousel_themestoreIn another Google+ post Brian provided tips on how to make your new themes invisible in the Play Store to devices not using the new Theme Engine. If you update one of your existing themes to the new Theme Engine but still want users to be able to install the previous version on their devices running the legacy engine, Brian also explains how to do that. Following his instructions lets you keep a version for the previous engine and one for the new engine under the same package name in the Play Store. For example, if you had a theme for the legacy engine called Project X and you updated it to the new engine, users could install the Project X for whichever engine they're running, and won't have to pay again for the updated version.

The most obvious incentive for you to submit your work to the Theme Showcase is easy discovery for your potential customers. The Theme Showcase acts like a Play Store lens devoted exclusively to themes (the pay links go to the Play Store, so no worries there). Also, you can release individual components as separate apps, so if you only want to do an icon pack you can just submit that without having to also include a boot animation, system theme ("Style") or font pack for example. It's another way to get exposure and reach the millions who will soon be using the Theme Showcase. It's never too early to get the jump on this opportunity.

Source (you'll have to join the CyanogenMod Theme Engine Alpha community to follow these links): Brian Resnik on Google+ (submission guide) (Play Store tips)