Ok so this is what I'd expect...
Malta is near Sicily (am I right? Because that's what the Internet says x3) and Sicily is in Italy so any Vivillon form said to be found in Italy I think you will be able to catch. Basically anything under the name Italy or Mediterrainean. For the locations and pictures of Vivillon they are right here just scroll down slowly until you see 'em!
Some reasons your Vivillon is may be Garden...
- Although your 3DS and you come from Malta, if the language is set to something else then it will think that you are there (eg: language is set to Japanese, the game probably thinks you are from Japan) and so the Vivillon are going to have a different pattern.
- It may be some minor programming location quirk or some big glitch effects
(Though I highly doubt thus because there are no glitches in X or Y)
- It may be Malta's actual native Vivillon is Garden, it hasn't been confirmed but it's possible.
So there you have it and of course...
Hope I Helped! =]