I love your little rental house...it's so cute, especially with the tin roof.
I can see adding lots of charm with a cottage garden...lots and lots of perennials up against the house. You might consider adding some low, evergreen shrubs for winter interest, and then putting the perennials in front.
I would just plant perennials in groups for splashes of color. Make sure the different perennials colors look well together. Vary the textures and heights, and I don't think you can go wrong.
I don' know where you live, which means I don't know your plant zone or your sun/shade conditions, so I can't recommend specific plants.
You might also consider a walk from the street to the house, if you want to spend the money. Center it on the door.
