Can't change Gmod background

i downloaded 5 backgrounds today,i tried replacing background01.vtf in materials\console folder,and i still have the same old background.why?

What resolution do you play on?

1280x720(native) 16:9 widescreen.i’v seen that in the same folder there’s a background_widescreen file,so i thought that it couldbe because of the resolution.so i renamed the new bg fril into background_widescreen etc,and still no avail

EDIT:ok now renaming both vtf and vtm files it works,although the resolution of the new background is very low and almost blurred.oh well…

Yeah the vtf and vtm are both required to be widescreen, for that resolution.

You will find it may be stretched and blurred because the background was intended for smaller resolutions and your widescreen monitor has stretched it out to fit.