"架上绘画" can be translated into English as "easel painting" or "panel painting" (though "panel painting" more commonly refers to paintings done on wooden panels specifically, while "easel painting" is a broader term encompassing paintings done on canvas or other supports typically placed on an easel).
In most contexts, especially when referring to the general category of paintings created for display on an easel rather than as part of architectural decoration or another context, "easel painting" is the most appropriate and widely understood translation.