Ryder, Some things to consider ......
You can absorb soundwaves - the density and composition of the materiel will determine what waves can be absorbed.
It is easier to absorb high frequencies, which have short wave lengths, and its easier to diffuse reflections with short wave lengths as well.
For example a rough surface on a canvas painting will effectively act as diffusor for very short wave lengths (high frequencies) which might be as effective for your purposes as anything else. But a painted canvas will not absorb any more frequencies than a bare wall which will not absorb or diffuse much of anything but is still preferable to glass which will absorbe and diffuse nothing. Painted canvas will not diffuse lower frequencies at all, but if your problem is first reflection points that might not be a problem as you are frequently just trying to control the high frequencies, an excess of which can cause a blurring (distortion) and a sense of brightness.
Using a cloth such as one having a heavy burlap weave will absorb very high frequencies and diffuse lower frequencies (thats why you should leave your speaker grills off your speakers if you want to hear your tweeters full potential).
Its all relative and, unlike a lot of audio that is not, it is based on hard science, not subjective. To effectively treat a room you must find the 'problems' than need attention and then figure out what materiels will work for you.
But to answer your question directly, IMHO a canvas painting will not absorb any high frequencies (except for those in a bat's range) and will effective diffuse only higher frequencies in the audio spectrum. Better than nothing and a hell of a lot better looking that audio acoustic panels! :-)
You can absorb soundwaves - the density and composition of the materiel will determine what waves can be absorbed.
It is easier to absorb high frequencies, which have short wave lengths, and its easier to diffuse reflections with short wave lengths as well.
For example a rough surface on a canvas painting will effectively act as diffusor for very short wave lengths (high frequencies) which might be as effective for your purposes as anything else. But a painted canvas will not absorb any more frequencies than a bare wall which will not absorb or diffuse much of anything but is still preferable to glass which will absorbe and diffuse nothing. Painted canvas will not diffuse lower frequencies at all, but if your problem is first reflection points that might not be a problem as you are frequently just trying to control the high frequencies, an excess of which can cause a blurring (distortion) and a sense of brightness.
Using a cloth such as one having a heavy burlap weave will absorb very high frequencies and diffuse lower frequencies (thats why you should leave your speaker grills off your speakers if you want to hear your tweeters full potential).
Its all relative and, unlike a lot of audio that is not, it is based on hard science, not subjective. To effectively treat a room you must find the 'problems' than need attention and then figure out what materiels will work for you.
But to answer your question directly, IMHO a canvas painting will not absorb any high frequencies (except for those in a bat's range) and will effective diffuse only higher frequencies in the audio spectrum. Better than nothing and a hell of a lot better looking that audio acoustic panels! :-)