I have been interested in creating custom colored items at some point. However the guide that is up did not seem to answer all my questions
When it comes to submitting an item for acceptance, can it only be from the available monthly items?
If it can be for other items in the Avi Shop, where are those downloads? (seems people can add more than one color to a color layer when customizing vs the given one color option for items that can be changed)

Also, is there an appropriate place for me to share customization edits for review (not selling/accepted)? Seems the Custom Item Sales and Discussion is mainly for selling.

Looking through more pages of the sub forum it seems customs of only the current month can be submitted, so I guess nvm on that.
But would it still be appropriate for me to play with past months' items and posting them for opinions/ possible crits?

I would post that in general discussion forum, but if you want to show examples and maybe how you work with it for future customs and if you plan on selling them, I would recommend opening up a custom shop as some people do.

Nice to see more people interested in creating custom items~ I always love obtaining others designs. =w=)~

Like you've already found out, you can only submit designs for the current month. I'm not too knowledgable about the entire process, but I believe you can get more copies of a (already submitted and accepted) design even after the month has passed.

While general discussion definitely does work for just showing ideas, I, personally would post in the Custom Item Sales and Discussion forum, as it's for discussion too. :3 It's really just a personal choice though I think. So either way. ^^

I don't think too many people play with designs from previous months, but definitely go for it if it interests you. Whatever is most fun ^-^ I'd definitely be happy to look at your designs, even if they are from previous months c: Some of the previous months items have been pretty cool too ^__^//)/

Good luck and happy designing :D