You could also scale the sprites that you use. in 3d game it is just normal, because when you move to or away from some objects the textures always scale. for 2d games, the sprites look best, when their texturepixels fits to the monitor pixels, beause you dont need to filter.
But to support multiple resolutions, you would have to use different sizes of the texturesprites. You can per example use 3 resolutions and have all of your texturesprites in 3 resolutions available also. this would look best, because you dont need filtering.
Ont he other hand you can just create the texturesprites for the biggest supported resolution and then you scale down the images for lower resolutions. I wouldn t give bigger resolutions a bigger viewscreen, that would be unfair (specially in multiplayer).
If you biggest resolution would be 1680, you could choose that as your raster.
1680 / 1680 = 1. So 1 of your ingame-size (per example meter) = 1 pixel.
If your spite should be 25 meter, you would use a 25 pixel image.
On a 1024 Resolution however, you have the following values:
1024 / 1680 = 0.61. So 1 Meter is 0.6 Pixel in your game.
The 25 meter sprite is then 25 * 0.61 pixel ~= 15 Pixel. So you simply have to scale all you intern values by a factor of 0.61.
