I already have an Everdrive 64 label that I made for myself. It isn't anything amazing, I didn't really try to get creative with it. I just tried to get the job done.
This is the one that I have on my cart...
Same label with different background:
Same label with different background:
Yeah... I really didn't spend any time with it. I already have an N64 label template, so I just simply put the N in there and embossed some "Everdrive 64" text. Then I probably did a Google image search for "cool background" or something like that lol. I still have the Photoshop file for it though, so if you want to link me an image to use as the background it would take me two seconds to do it.
As for the Sd2snes and Mega Everdrive, I don't have labels for them since I don't own those carts. However, I have SNES and Genesis label templates made up already, so I could make them quickly. Any suggestions? Or do you want me to just do whatever? The only thing is, since I don't own those flash carts I don't know where the card slots and buttons are. I can guess and give it a wide birth though.
I might have an NES label template, and if I do, same story. I could make one easily. The SMS on the other hand, I don't own the system or any carts for it. I don't have a template for the label, and I can't even create one since I don't own a SMS cart.
For all of these tho, there's gotta be TONS of uploaded labels out there.