Schwall was previously chief executive of Springer and Jacoby, a European creative agency based in Germany.
He joined the company in 1999 as client services director and became managing director and executive director, before being promoted to chief executive in 2005. He has experience of working with clients and brands across Europe and globally.
At Media Square, Schwall will be responsible for developing the company's presence across northern Europe, excluding the UK and Ireland.
The northern European operations will build on Media Square's established businesses in Germany, which include the advertising and marketing group, SEA; the advertising agency, Hoffman Schalt; the public relations consultancy, SEA PR; and the corporate branding consultancy, Muth SEA.
All of these businesses will report to Schwall.
Roger Parry, chairman of Media Square, said: "We are very committed to building and strengthening our operations in northern Europe and, in particular, to building on the already well established base of businesses in Germany."
Schwall said: "Media Square already has good businesses in Germany and I very much look forward to working with the management teams in Dusseldorf and Frankfurt to take these businesses to the next stage of development."
Earlier this month, Media Square reorganised its business into three divisions -- Advertising/PR, Marketing, and Design.
In the UK it owns agencies such as digital shop Twentysix London; direct agency Clark McKay & Walpole; and Wax, the result of the merger in September of three Media Square companies, Catalyst, Dynamo and Theatre.