I am late but;
1. Add my own trainer GIF and image (and other info).
If you create your own, you have to create a GIF and a face and otherwise choose from the standard ones. Also, let us name our trainer and pokémon, etc.
You can choose and change the trainer's avatar in the PC, but I think you already know that seen you have a Lass as your avatar. There's a thread to create your own trainer, specifically animated, but it's expected that you'd make it, with a reward for your contribution, and the Trainer been implemented in rmrkmon. There's no need to name trainers, since, their, well, us. There's no point in naming pokemons, since their just there for collecting purpose.
2. Show my trainer info in my signature by checking on (or off) a box option.
It shows your GIF, face, name, party pokémon, amount of PM cought, etc.
You can link your avatar & Pokemon team in your signature, the rest kinda seems unnecessary in my opinion.
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3. Create a pokégym, shop, trainer, pokécentre, etc. (involves a currency) -> Make a huge pokéworld 
Depending on what you want, you can work or battle for money. If you have enough money, you can open a shop, pokégym, pokécentre, day care, etc!
That sounds too ambitious . . . too ambitious for a simple collecting game. However, there was someone around who was working on a Pokemon Game Project, and wanted to try to implement the data from the member's rmrkmon's pokemon data into his game, not sure if the guy is still working on it or which thread it is, but that's the closest to this there is. There's a Pokemon map making contest around too, and one to make a custom field, with the costume field been the closest to what you want for customizing your gym/house/etc.
4. Use and create items to use for upgrading your pokémon, decorating a house/gym/shop/daycare and use them in battles.
What it said above (also recipes and etc.)
The game's just a collection game. Those add-ons sounds more like they belong in the third suggestion. And I already answer most of these above. I don't think there'll be a battle system for it, as such would require to make skills, lvls, items, etc. this has been answered before a few pages back.
5. create your own pokémon!!
This may be a bit overboard, but I'd like to be able to see people to create their own set of pokémon which have to be voted into the list.
Not gonna happen. It's been said before; only official pokemons would be implemented (Currently Gen.1 to Gen.6), excluding Mega-Evolutions & Special Forms. It has to do with how pokemon are implemented by numbers in the script for simplicity.
This ain't neopets dawg.
No, is pokémon but would be awesome to earn money with posting and get to do something with your pokémon besides trading and collecting
That's the point of the game, it's just a trading & collecting game. And remembering about it, it's worked and was very addictive, and fun to trade with others.
I don't see what you mean by earning 'money', whether you mean some kind of fictional currency (which, to be fair, the point of Pokemon Trading kinda aside from making users have to trade with others, was in it's way an already established Currency (?)), or use actual money (Which isn't a good idea for various reasons.)
And to move on something on here, I found a
but it ran away ;__;
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