So we have Bronze, Silver and Gold for talismans so far. This is one suggestion I have for another level of difficulty: platinum or diamond, which is a light-blue disc (around the region of RGB 0, 255, 255).
The reason for this one is because some of the talisman suggestions that are coming in for Revenge of the Lemmings are beyond difficult, like "The Floodgates Open - complete in under 3 minutes." would be so much harder than the other Gold-level talismans. Either that or the pack creators should just re-scale their difficulty ratings a bit more.
Not sure if it's worth it or not, but it would be nice to have the option.
personally i like the idea, to add challenges that are harder than gold level achievements
I wish i had time to make the talismans, like an idea of what they look like
I am not a real achivement fan in Lemmings (that's why I don't care about them in my own packs) and I think that the current bronze/silver/gold distribution is completely enough.
Maybe the "gold" achievement should really be reserved for extremely hard ones only and not be given away on medium challenges.
If someone really sees a need to have four or five different levels of achievements within a single pack, I could consider it (it wouldn't be hugely difficulty to implement - those who've made packs with talismans might know that there's already a fourth type, "hidden", which doesn't show up anywhere in game but can still unlock a secret level); but currently, I think three is fine. It's fine if Pack A's bronze talismans are as hard as Pack B's gold ones, etc; saying that "gold talismans should be of similar difficulty in all packs" is like saying "every pack's final level should be of similar difficulty".
Since there's no further input on this, I'm going to close this discussion now.
Final decision: Talismans will remain as only "Bronze", "Silver", "Gold" or "Hidden".