As Emmanuelle has said: the image search has steered you seriously wrong. There’s a better way. Since more than half of English words are from either French or Latin (the mother language of French), there’s a better alternative to flashcards. Simply look “sombre” up in a dictionary and you’ll notice that there are a few definitions, some (the figurative ones) of which match up with the English word “somber.” At this point, it should be easy enough to remember the literal meanings in French (poorly lighted or dark in color). 

Any good dictionary will also point out that the word comes from sub- (sous) + umbra (ombre) — literally “under the shade.” Notice that English “umbrella” means literally “little shadow.” (You’ll also learn the word “ombre” at no extra charge.) Read the sample sentences out loud, repeat them with your eyes closed, and use them as a guide to make your own sentences. Your done. No finding irrelevant images online. No downloading images. No making, studying, or reviewing flashcards. 

Voici les sens figurés que j’ai trouvés dans le Wiktionnaire. Tu vas remarquer que même les mots utilisés dans les définitions sont des amis, alors, c’est une excellent occasion d’apprendre aussi ces mots-là en même temps: 

(sombre)

3. Qui est mélancolique, morne, taciturne ou chagrin.

4. Qui est inquiétant ou menaçant.