If you look into the various threads here in Denial where I posted examples for MINIGRAFIK, I
usually followed up "teaser" pictures with the programs that produced those screens. Unless those pictures were the result of manual work in MINIPAINT, and obviously no such program existed (I'd then still attach the corresponding MG file).
I did so without necessarily being asked for, merely I think it's just illogical to post something along programmed computer art into the
Programming section of a Forum without following up with the program that did the feat. Regards "gauging the interest": with a hobby as obscure as ours one needs a good lot of instrinsic motivation anyhow - you'll fare much better getting responses for your VIC-20 work here in Denial than in any other related forum. But you should be at least a little more consequent.
So it's up to you: you attach the programs here in the threads, and you
might find people here obliged to say something about those programs, follow up, improve them, spark new ideas, whatever. Just those static screens probably aren't going deliver enough incentive for this. My thoughts already.
And regarding the
file type best suited for attachments, just
look around what's usually used in the forum: you'll find plain
*.d64 files, *.prg or *.d64 (or other storage image file types) archived in
*.zip, etc. - unfortunately, plain *.prg is disallowed by the forum software for whatever reason. On the contrary, *.7z and especially *.rar are extremely, well, rare. *.zip is supported out-of-the-box in all Windows installations since XP, it is also a standard archive format with all Unixes (that includes Macs, iOS and Android) so there's no good reason to use yet another compressor unless for specialist needs. Programs (or parts thereof) in text form should be posted in code-tags, that should go without saying. Etc.