Here is an almost sure recipe to get a good look and feel for a presentation template, even with an Arial font:
- One nice accent colour, but used sparsely for only that: provide an accent
- The other objects in shades of grey, using relatively more light ones than dark ones
- Text in dark grey, not black
- No lines around shapes, let the color (i.e., grey) do the work
- Everything flat: no shadows, no gradients, no reflections
- Black & white images only