it is not about the size, because I made smaller pack than my first one as a test and it would also black out the iconsHave you tried making smaller theme packs at a time? There's probably a limit on how many themes can be in a CIA before the 3DS acts weird about it.
I have messaged Redunka if they could make a pack for me, will see if I accidentally exceeded some limit (although I am unsure that is the case, there is like maybe 70 themes in the pack or something like that and isn't the limit 100 themes?