Some suggestions from other metas:

DIY: http://meta.diy.stackexchange.com/questions/549/change-the-image-upload-so-that-a-thumbnail-is-shown-and-the-full-size-image-lin

DIY: http://meta.diy.stackexchange.com/questions/369/please-try-using-smaller-versions-of-images

GD: http://meta.graphicdesign.stackexchange.com/q/935/8708 (already requested [here](http://meta.stackexchange.com/questions/92568/allow-svg-image-uploads/273910#273910) as mentioned in the OP)

Some bugs from other metas:

DIY: http://meta.diy.stackexchange.com/questions/1009/built-in-image-uploader-falls-over

I've made this CW to make it easier for others to add more from their own meta.