You know what's cool? Having little bits of your fursona that you can carry around with you and show off. You know what else is cool? The SEGA Dreamcast.
How about we combine the two? I'll show you how to make a cool as fuck VMU conbadge like this:
Okay, strictly speaking, it doesn't really work as a conbadge. You can't take the VMU out, put it on a lanyard and show off the icon, unfortunately. Maybe someone will come up with some homebrew to do that at some point, but until then, this will show up when a VMU is inserted into a controller when the console boots or is in the settings menu.
So, step 1 is to design the icon beforehand. You could do it all on the Dreamcast software, but it's a little unwieldy and you'll probably appreciate the use of more comfy technology to do the initial designing.
The VMU icon size is 32x32 pixels, and uses 2 colors - on and off. Some official icons use some pretty creative means of making other tones, but you're stuck with just those two colors. Here's some icons from Sonic Adventure 2 for reference that make some good use of technique:
I'd recommend using a simple bitmap editor like Microsoft Paint, but there's a lovely little mobile app called Dotpict which has some great features, and it has the advantage that you can doodle away at it whenever you have your phone with you.
Once you've designed your icon, download an app called Dream Explorer and burn it to a CD-R. I'm not going to go into detail about how to burn discs for Dreamcast, as your mileage may vary - but burning at the slowest speed possible usually yields the greatest success, and there are plugins for ImgBurn specifically for burning CDI images.
Dream Explorer is a great tool in general, and I highly recommend keeping it around for features such as unlocking more VMU space or copying save data / DLC from the database on disc.
In Dream Explorer's menus, select the "Extra Icon Editor" option for the VMU you want to draw the icon onto. You'll be presented with a screen that allows you to painstakingly recreate your image pixel by pixel onto the Dreamcast screen. Not super fun, but you can check how things are looking on the VMU as you go!
Once you're done designing, press Start to save the icon to your VMU. You might get asked if you want to install some kind of special menu when you save, but I couldn't see what effect this actually had whether you chose to install it or not.
It'll take a couple of seconds to write the data, but you should be done!
There's a little, somewhat disappointing quirk to doing this, in that the icon that shows up on the console screen is a generic "VMU Tool" one rather than your custom design. I think the only way to change this is by desigining the icon in a way that transfers files from a PC to a Dreamcast, which is a fair bit more complicated and resource expensive. If I find an easy way of changing this icon, I'll make sure to update this article with information.
For now though, enjoy seeing your little critter show up on the VMU!