Yay suggestions :3 MA has a thread like this, you may want to check it out for some ideas. :D I'll pull out a few goods ones since the topic is fairly long

And I agree with the gender swap :3

Randomo ideas:
-Reset (ie level 0, clicks 0)(I ran a poll once on an old MA site that I had and a surprising number of people liked that idea O: )
-Items that have no purpose, only meant to be sold
-Going to quote cuz it's a lot XD -Instant max level
-Here another quote I picked out:-Pet backgrounds (not sure if this is possible XD)
-Another quote XD Interesting stuffs I pulled from that topic :3

Well I am replying to Gigi's post now, it seems that she has some interesting ideas to share.

Reset Clicks/Levels: This can be done easily, I will add it for Mys v1.3.0 now that you asked.
Items that serve no purpose but to be sold: It is already available for the itemshop script I made. Such items are called valuable items, you usually get them by using exploration system and then sell for money.
Instant Max Level: Similar to Reset Clicks/Levels, just a different extreme I guess. Will add it for Mys v1.3.0 too.
Level-based Restriction: Sounds like a good idea, it is quite similar to species or usergroup-based restriction, I will give a try.
Chances of items taking effect: I like it, will give a try too for Mys v1.3.0 prior to its official release.
Chances of amplifying item effect: This should not be difficult, but I do not see a point of including it in an official release. May consider this as a Mod if demand is high.
Alternative outcomes for items: Good idea, it may be a tedious(not difficult) to handle for Mys v1.3.0, but I will consider for future releases.
Limits: Chibi suggested the feature of item promo code, I will add this soon.
Pet background: Umm this may be difficult, since it will need to merge the background and pet image. I personally never tried that before, but Anna has done that with her breeding script. I will see if it will work nicely.
Create/Cure Illness: Well this is planned for future releases of Mys v1.3.x series, since we will need an adoptables status/sickness system as prerequisite. Good point btw.
Turn your adoptables into different species: This is just like an evolution system, isnt it? I will release an updated version of adoptables evolution script following the release of Mys v1.3.0, and evolution items will be part of that Mod.
Corrupt/Purify Adoptables: Dont understand what that is, mind elaborating?

Items that let you upload a custom pet image? :3

Pet Background I assumed it might be difficult seeing as very few other adoptables sites have a feature like that (I can only think of two off the top of my head O.o). But an idea is an idea XD
Different Species I believe the suggestion more entailed changing the species entirely. Similar to how on VDex if you have a Ditto and use a Metronome on it the Ditto will turn into a random Pokemon. Something not evolution based though, coding-wise, I guess it does sound very much like evolution except it would have multiple outcomes of what it could turn the creature into. So in that case it just seems better to give "evolution" items the ability to have more outcomes. :3
Corrupt/Purify I believe the user who posted that was going on something similar to the sick/cure items, except it would change it to a new image to display the new effect. So, in that case, I'd think it'd be an item that just changes the pet's image to another one. Giving the effect that your pet has become "corrupted" or "cleansed". It could also be used for many other things, similiar to Neopet's Paintbrushes or whatnot. :3

An item that lets the user change their name.
an item that would would give out a random promo code from a list you have per-set.

@ Gigi: I see, thanks for bringing these up to me. I believe many of the request features will be added for Mys v1.3.0, while others may be available in future releases or as Public/Premium Mod.

And, an item that changes an adoptable into a different species...Lemme think about it then, still believe item based evolution can achieve the same purpose.

@ Chibi_Chicken:
An item that allows users to change their usernames? Should the item be a consumable item(that its quantity decreases by 1 each time used) or not?

I would suggest it be a consumable item and along the same lines build an item that lets user change their pets names, so they can use some of that money they have been saving up.

Cyanide pills to put down your pets! Definitely consumable but available in bulk.

But on a more serious note pet deletion/release items? Admin could call it w/e lol :D

An item that changes your pet's image to an alternate (like zombies).

@ Chibi_Chicken: Alright, I will take a look into these. It seems that users can change the names of their pets at any time for now.

@ Nemesis: Are you referring to the disabled feature to kill pets? Also pet release can be achieved with the pound feature, unless you want pound adoptables to be globally turned off and only users with pet release items can pound their adoptables.

@ Teshia: I believe alt image change is already available:

If you have a different suggestion regarding alternate image items, please lemme know.