The Indianapolis parks department is renewing its call for nonprofits and companies to propose partnerships that could relieve budget pressure while adding amenities to the sprawling park system. After years of stagnant city budgets, parks officials see public-private partnerships as the most likely way to expand park offerings or improve programs. Outside operators already run the Major Taylor Velodrome complex, city golf courses, a couple after-school programs and a zip line course at Eagle Creek Park. … Key considerations, city officials say, include whether a partnership would reduce the city’s costs or bring in income. That’s because the parks system is saddled with a nearly $46 million backlog of improvements at its facilities that can’t be erased by its annual $3.4 million capital budget. Indy Parks also has a $51 million wish list for new facilities and offerings that are unlikely to be covered under the current budget.