We use boxed images of our Virtual TimeClock software on our web site even though 99% of our time and attendance software is sold digitally. I don't have empirical data to demonstrate that it is 'better', but it is consistent with the online philosophy built around metaphors.
The entire economy of selling bits and bytes as a software product falls apart if you take a moment and reflect on the cost of goods sold. For software, that number is for all intents and purposes is zero. Looking from this perspective alone, a 'reasonable profit margin' would lead to most software prices being very low.
On the other hand, if you factor in the utility and possession of a useful bit of code, it is absolutely appropriate to think about software as a tangible product. So it makes good sense to reinforce the idea of selling intangible bits and bytes as a product that goes into a box. (As an aside, this disparity between utility and cost of good solds is why software has made men like Larry Ellis and Bill Gates so incredibly wealthy).
The online world has been created largely around building a connection between the digital and real. The concept of an icon is something that represents the function of your code when it runs. We refer to our screen as a desktop. We 'save files' (visually and mentally) when in actuality we're magnetically charging portions of a spinning platter. We delete files by putting them in a trash/recycle bin that doesn't even remotely exist.
Reinforcing the connection between the digital and the real is something you're already doing as a developer. Why not extend that thinking consistently to your marketing?