High Res Images

Ideally, outline rendering should be turned off, but if the image in question shows enough detail, then a single pixel border shouldn't be a problem. In most cases, items show up fine if the outline is off. However, it can be used to separate items if they are all a single shade of color that matches the clothing or to show the sleeve of items if the sleeve appears to blend in with the clothing. Outline rendering should not be used if the items would appear to be too small, or the zoom was not sufficient.

as for High-res, if the image becomes too big, it may cause loading errors. Ideally, large images aren't used unless it is for world maps. I don't mind it, but if it's too big, then it'll take up server bandwidth or something (I'm not familiar with this :x)