A problem I often encounter when a search becomes difficult: I don't know the exact spelling, or I don't know the common term the thing I look for usually is referred. So I try to think of something related. For instance I recently was searching for a german entrepreneur who is popular for his social engagement towards his employees but I totally forgot his name and the name of his company. But I remembered him from a Youtube Video, there he flew with a helicopter, so my successful search term (in german) was a after experimenting with a few terms: textile employees entrepreneur social helicopter
Another tip: Switch search engines and use other web pages as search engines by reading them or using STRG-F. For instance you know how to get near the topic. Use the above method but afterwards click on some links and read them. Think about the content and ask yourself: Is this kind of web page more close to the result I am looking for than the web page (result page) I was browsing before? Yes? So change your search term and incorporate terms or "figures of speech" shown on this page. You will probably get to a similar page that might be even more relevant.
If you are looking for video content it makes sense to search on Youtube. But beware: Google search is better ;) So consider the last described tip and switch between Youtube and Google. For instance once I was looking for a funny video of some guy. After some "switching" I found his name, continuing I found the name of documentary and finally I got the video clip I was looking for...
By the way regarding this painting: If you are still not successful on Google, try to find a forum of art enthusiasts that might know this painting. That way I once found a song very quickly. (Though I already knew the forum, though I never used it before...)