@ weltall:
1) inconsiderate generalization: would you bet on every person worldwide having a broadband connection?
2) unnecessary accuracy = low efficiency (*)
JPEG as such is still rather convenient, especially for images with limited detail sharpness and color saturation; it just requires a bit experience in optimizing size versus quality loss.
Screenshots made by PlaneShift in JPEG format have a quite low quality (I believe, default quality value is 75 of 100). So it is obviously and objectively recommendable to have PlaneShift save screenshots in lossless PNG first. But for presentation in the World Wide Web, a moderately compressed JPEG (quality 95 .. 90) is still a good compromise, preferably in "progressive encoding", and if available, even with "macroblock-adaptive quantization" (JPEGOpt / JPEGmini); and if you have saturated red or blue areas which start to look fuzzy, you may even try to disable "chroma subsampling" (in JPEGOpt: "Extra color").
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(*) May I remind you on the "voiceover" requirements? Which combination of consumer soundcard with 16-bit DAC and consumer electret microphone is at all able to record samples in 32 bit depth and 96 kHz spectrum?