What format is the image you're using (I'm guessing .jpg) and what is the actual resolution? The file size for compressed images doesn't matter because it must be decompressed by TG to be used, so it's the uncompressed size that will impact the system, and this directly corresponds to image resolution. It also matters greatly what resolution you're rendering at. It doesn't look like you're rendering all that large (1280x960?), but that also has an impact on memory.
Ultimately the ability to handle complex scenes and render at high resolutions should be improved. But it's almost important to realize that the definition of a "complex scene" isn't necessarily what you might expect. It's what is complex and difficult for the renderer that matters, not necessarily just how much "stuff" you have in the scene.
- Oshyan