I would consider the "source code" for artwork to be the project file, with all of the layers intact and whatnot. The Photoshop PSD, the GIMP XCF or the Krita KRA. The "compiled" version would be the exported PNG/JPG.
You can license a compiled binary under CC BY if you want. That would allow users to freely decompile/disassemble it or to bundle the binary for their purposes, but it's different from releasing source code. It's closed source, but under a free license.
So the cover art I made for a friend's album isn't open source, even though I released it as CC BY-SA... because you can't make it yourself?
I would consider the "source code" for artwork to be the project file, with all of the layers intact and whatnot. The Photoshop PSD, the GIMP XCF or the Krita KRA. The "compiled" version would be the exported PNG/JPG.
You can license a compiled binary under CC BY if you want. That would allow users to freely decompile/disassemble it or to bundle the binary for their purposes, but it's different from releasing source code. It's closed source, but under a free license.
you released it under a non open source license. So very clearly: no it is not
Wut. That license is literally compatible with the GPL
CC BY-SA is considered open source. CC BY-NC is not.