
My goal is to get one of every Japanese card released. These are my focus since they have more unique cards than the American releases.
DPt4: 映画公開記念ランダムパック2009 (Movie Release Commemoration Random Pack 2009): Sheena's Dialga
Source: Callyfin of Collectorviper
This is part of the special 12th movie card set featuring Pokemon with their trainers. Callyfin managed to get a spare of this Dialga, and kindly traded it to me!
Meji Promo (from chocolate packs)
Source: Hardrock-Pokemon
There are a great many cards distributed as Meiji chocolate promos. Here's Dialga's!
Diamond Collection Set Promo
Source: Yahoo! Japan
This card is part of a Dialga-centric Diamond collection set (which I still need to pick up). It matches the art on the US version of the Diamond and Pearl set.
Mewtwo Collection Pack Promo
From a set of 12 cards, including a Mewtwo Lv. X. I managed to grab this one singly, though!
Booster Pack Promo
Source: Daiei (Shiki, Japan)
With the 11th movie new card set, came new booster packs. And with a purchase of a few of those packs, you could get a promo card! I chose this one, of course.
Dialga vs Giratina Theme Deck Promo
Source: Daiei (Shiki, Japan)
One of two promos in an 11th movie starter deck set, the other being a nifty origin form Giratina promo.
Intense Fight in the Destroyed Sky (DP6) Dialga
Source: callyfin of pkmncollectors (also runs collectorviper)
11th Movie Card Set Promo
Source: Movie Theater Promotion (Ikebukuro, Japan)
It's hard to choose, but this is one of my favorite Dialga cards (and images in general). It fits neatly with the 11th movie itself, and the art is just really pretty ^_^
ギンガの覇道 (Galaxy Conquest) - Dialga G Lv. X
Source: eBay
A beautiful card that came out poorly with my scanner. ^_^;
ギンガの覇道 (Galaxy Conquest) - Dialga G
Source: Yahoo! Japan
The base card that goes under Dialga G Lv X.~
McDonald's Promo (Japanese)
Source: eBay
I was really surprised to find this promo from a Japanese McDonald's on eBay. Yay for more Dialga cards!
Entry Pack Promo
Source: Yahoo! Japan
Another all-over foil that wasn't captured well by my scanner. A very nice looking card, though!
Dialga Japanese DP1 Theme Deck Promo
Source: The blue Dialga theme deck below!
I'll usually pick these cards up if I see them for sale, but I'm not dead set on getting 100% completion of them.

Jumbo TCG Promo
Source: Target
From the Dialga Premium box set, comes a Jumbo version of the promo below. I know there are many out there, but this is my first jumbo TCG card, and it's beautiful!
The smaller card that was included with the big premium box set.
Dialga Lv. X Promo TCG Card
Source: Dialga Platinum Version Promo Tin (see Cases)
Dialga Lv. X Promo (Platinum Version)
From the Platinum version of the tin, which features Giratina and Shaymin on the other sides (rather than Palkia and Darkrai).
Platinum: Dialga 23/127
Another card from a Japanese promo set that was tossed in with Platinum!
Platinum: Dialga G (and Reverse Holo version)
The US versions of the Galaxy Conquest Dialga G. I don't have the Lv. X of this card in English yet, since it's still a bit expensive due to its use in tournaments. I'm content to wait until it's no longer viable there!
Platinum: Holo and Reverse Holo (6/127)
In the Japanese set, this was part of a promo pack, but here it's just thrown in with a regular set.
Platinum: Holo and Reverse Holo (5/127)
Majestic Dawn: Dialga (and reverse holo)
Supreme Victors Poster Pack Promo (DP Promo 49)
This one is from a small promotional pack sold in stores - not quite as exciting as the shiny card portfolio the Japanese version was included in and sold at the movie theater!
Great Encounters: Dialga Lv. X
Source: fernchu of pkmncollectors
Great Encounters: Dialga
Source: Great Encounters Theme Deck
This is the version that came in the Great Encounters theme deck (shown below).
Dialga Lv. X Promo TCG Card
Source: Dialga Promo Tin (see Cases)
From the early Diamond and Pearl collector tin. I like the "my claws, let me show you them" pose.
Diamond and Pearl (DP1)
From the first series of the D/P TCG. Pulled it myself while
drafting this set! I'd like to get a better scan of this, but I'm not sure where in my house it is...
Not shown: Reverse-holo version of this card.

Great Encounters: Time Theme Deck
Source: Target
It's not all Dialga, but it came with the promo card and the coin, and features Dialga on the cover (and no one else), so why not?

Dialga Japanese DP1 Theme Deck
Source: Pokemon Center (Yokohama, Japan)
Sure, I had the coin already, and the card in English, but the set is a neat item in itself (and so sparkly!)

Dialga Premium Box TCG Set
Source: Target
This card set includes a few special Dialga cards, but the set on its own is a nifty collectible too.
Trading Card Game Cases (DP, DP, and Platinum)
Source: Daiei (Shiki, Japan), Gamer's Paradise, and Target (all retail stores)
These are the booster packs that I know of that feature Dialga: Diamond and Pearl (US and Japanese versions), and Platinum. I'm probably missing a bunch more!