Make background of a date multicolored or insert an image about xamforms.controls.calendar

[rebeccaXam]

Use BackgroundPattern of a special Date, theBackgroundPattern(1) the 1 means 1 Column.
I will update the wiki as soon as I find the time ;)

SpecialDates = new List<SpecialDate>{
					new SpecialDate(DateTime.Now.AddDays(3))
					{
						BackgroundColor = Color.Green,
						TextColor = Color.Blue,
						Selectable = true,
						BackgroundPattern = new BackgroundPattern(1)
						{
							Pattern = new List<Pattern>
							{
								new Pattern{ WidthPercent = 1f, HightPercent = 0.25f, Color = Color.Red},
								new Pattern{ WidthPercent = 1f, HightPercent = 0.25f, Color = Color.Purple},
								new Pattern{ WidthPercent = 1f, HightPercent = 0.25f, Color = Color.Green},
								new Pattern{ WidthPercent = 1f, HightPercent = 0.25f, Color = Color.Yellow}
							}
						}
					}
}

[rebeccaXam]

In version 1.0.1 you can add a background image in SpecialDates:

calendar.SpecialDates = new List<SpecialDate>{
	new SpecialDate(DateTime.Now.AddDays(4))
	{
		Selectable = true,
		BackgroundImage = FileImageSource.FromFile("icon.png") as FileImageSource
	}
}

Note: Only works in Android and iOS for now