You can use the ((Album cover fur)) template. Please make sure the fill the "use" parameter. The most clear-cut case is a cover used in the infobox in the article about the album it illustrates ("Use = Infobox").
Skip images larger than 300x300 or explain why there is a need to use higher resolution in the rationale. Alternatively, you can reduce the size of the image and re-upload it. Note that the 300px limit is only a rule of thumb taken from this note.