Gartner was born in Winnipeg, Manitoba, but moved to Calgary, Alberta during her early childhood.

Her paintings, often inspired by subjects in old photographs but manipulated to "create scenes which can challenge a contemporary viewer", have been variously described as "disquiet" and having a "haunting quality".

Deirdre Hanna wrote the following about Gartner: "Award-winning essayist, Alberto Manguel, put Calgary-based Winnipeg native Marianna Gartner in the international limelight when he chose her as the only Canadian artist to profile in Reading Pictures, a 2002 book that also looks at paintings by historical giants including Pablo Picasso and Caravaggio.

For her first solo show since that book's publication, Sable-Castelli's Stepping Out, Gartner pulls back from the tattooed babies and circus freaks that first caught Manguel's attention.

"Gartner's fascination with Victorian curios is very much in evidence in these near-monochromatic canvases, and as her references get more subtle, the parallels with John Tenniel's illustrations for Alice In Wonderland become more apparent.