Can I reduce or make the file size smaller on a picture?

Of course it's possible, with almost every painting program. But first I'd like to say that it's a bit strange that it takes forever to upload a 600kb picture / icon. That should be done in like 2 seconds.. If you want to make the picture smaller you can use MS Paint or my favourite program Paint.NET. If you use MS Paint, open the picture with Paint, and click "resize". Then you can choose how much smaller you want to make the picture, in percent or pixels. (And of course save the picture after you resized it) If you use Paint.NET it's actually exactly the same, only the option "resize" is under "Image". Good luck!

If the icon you have created is 600kb then it is probably in bmp format and you need to convert it to a gif or png. The dimensions of the image can also increase the volume size so make sure it conforms to the requirements prior to uploading. Icons are rarely larger that 1cm x 1cm so you may need to consider whether your "icons" are actually icons or just little pictures. An icon usually has the "ico" extension. Only Photos should have jpg extensions and graphical art uses gif extensions although png can apply to both formats.