The current say so is as long as the gear's the right material (IE Mail,Cloth,Plate) and not Silly looking like the frying pan Weapon, you're fine.
The gear also still has to have stats aside from armor on it. That means that there are a lot of white or grey items that might not be available initially when Transmogrification goes live.
As an aside, a lot of people have been asking about hiding shoulders, belts, etc. For now, it's looking pretty unlikely that we'll offer the option to hide anything aside from helm and cloak.
Honestly, how can you offer the option to hide cloaks, but not shoulderpads?
The shoulderpads that have been added are getting bigger and bigger. Have you seen the shoulderpads of most class tiers on Night Elf Males? Their head is like half the height.
Anyway, a question I haven't seen answered: When you transmog, is it the slot, or the piece of armor?
As in, if I turn my Heirloom Shoulders into... Tier 1 shoulders I got doing a level 60 raid. Then I hit 80, and switch to a leveling shoulder, will it show the tier 1 shoulders, or the leveling shoulders?
And if you vendor a piece that you used to transmog the item to (tier 1 in the example), would the transmog break?
I'd like to provide an update on this statement I made. It turns out that Heirlooms will be eligible targets for Transmogrification.
Also (and this applies to all Transmogrified items), trading, mailing, auctioning or depositing an item in a guild bank will remove the Transmogrified art, returning the item in question to its original artwork.
So, while you won't have to stare at the same old Heirlooms the whole time you're leveling, you won't be able to send a set of Heirlooms that have been Transmogrified with tier 13 art to your level 10 alt.
just giving an example - can i transmog Repurposed Lava Dredger to use this Reclaimed Thunderstrike?
as a feral druid - we are stuck using a 2h mace as heirloom, which at present 2h maces are no longer designed to cater our spec
though i like to see the heirloom itself get fixed, i'll be happy enough if i can give it a more fitting outlook
No. No maces can be changed into Polearms. The only weapons that can be swapped between are guns, bows, and crossbows, because they are all classified as "Ranged".
The Mace doesn't have to be USEFUL for you to transmog to it. You can transmog an agility mace to look like a strength mace, it won't have any effect on the actual stats.