What does a “logo” means in sales/business talk?

"New logos" is the opposite of "existing accounts" or "current customers"

Examples:

How many new logo accounts do you need to land in 2014, how much will you to invest to achieve your objectives, and what can you do to get more bang for your buck?

Landing new logo accounts is essential to the health of any business. As hard as we try to maximize the potential of existing accounts, there will be some natural attrition over time as personnel and priorities change.

(http://blogs.richardson.com/tag/new-logo-accounts/?vid=null)

They are focused exclusively on new logo acquisition. They are not selling to current customers and they are not managing relationships.

(http://www.salesbenchmarkindex.com/bid/58855/Go-to-Market-Strategy-The-Hunter-Misconception)

You can also search for "new logo sales" on Indeed.com, for example, to get more context: http://www.indeed.com/jobs?q=new+logo+sales&l=

When you see a Championship League interview, a player or a coach is being interviewed in front of a board with many logos of sponsorship companies. The more logos, the more financial support for the league.

When a company, especially financial firms, makes a presentation material, they put logos of their clients in the cover so that they can illustrate their capacity in dealing with very famous companies. The more logos of globally well-known companies, the more prestigious and reliable the company would look.

"Logo" simply means:

A symbol or emblem that acts as a trademark or a means of identification of an institution or other entity.

New logos can mean new clients as you acquire the right to put their logos on your presentation or promotional material when you establish new relationship with them.