Cool, way to be proactive! This should be helpful for creators our there who want to put their best foot forward on both the web and mobile apps.
Obviously there's a lot we're still working on (especially apps-wise), so things like being able to edit your series banner image/position, profile pic, profile banner image/position, etc. haven't made it in yet. Those should give creators and readers a much better degree of control and customization in the app once they're baked in. However, as you can probably guess, there are a bunch of important bits we're working on first... things like improving the main feed, adding an activity/notification tab, and other "big" items. For now, your approach of trying to make something that looks pretty good on web AND in the app is a good way to go, as the customization features are probably a little ways off.
Couple quick details to help out:
For banners with a pattern, collage, or other artwork this is less important, but if you have text, important details, or if the image is balanced in a particular way (for example, with a title/logo on one side and a character bust or cast on the other), aligning things based on those left/right margins may help things look better. Of course, on very large screens or window sizes the banners zoom and stretch out, but it's a good starting point and generally works better than having important bits at the extreme left or right edges. Also keep in mind that the top and bottom edges will be the first to get cropped when the banner starts to zoom/stretch.
The use and style of series banners is completely up to the creator/owner of the comic, of course, but was originally intended primarily as a background image (for branding/personalization/theme/color scheme), and less as a billboard for critical text or other info. However, your example (with short intro and update schedule) is really very nice, so there are obviously ways to accomplish both. Unfortunately, the fact that the aspect ratio of the mobile series page is different (and that it's really intended as a background, especially on mobile) will continue to introduce challenges and the need for compromise, until we're able to let you set or adjust the mobile version independently. Basically, unless the banner is very simple it probably won't look "perfect" on both platforms at the same time.
Ideally, in the future you'll be able to at least move/scale the banner to set the default view... such that even using your current web banner, you could end up with something like this:
Still not perfect, but pretty good (also just a quick, hacked mockup without any tweaks or adjustments : )
- The huge variety of device sizes and pixel densities (particularly on Android) further complicate things in terms of trying to get a pixel-perfect look across screens... but based on the current image ratio, zooming/cropping, and base size of the banner, here's a rough guideline/template for what will show up on web vs. mobile:
This works really well for banners like Satan and Me and Geomagnetic, decently well for those like Mary Deathand Les Normaux... and unfortunately not particularly well at all for banners with your layout, despite looking good on the web.
Hope that helps!