Merge 2 images with node.js?
You might need this: https://github.com/zhangyuanwei/node-images
Cross-platform image decoder(png/jpeg/gif) and encoder(png/jpeg) for Nodejs
images("big.jpg").draw(images("small.jpg"), 10, 10).save("output.jpg");
I do no have enough reputation to add a comment, or else I would to Schmidko's answer.
Sharp works well, however, overlayWith is deprecated and you instead need to use composite. See below:
sharp(path + 'example.jpg')
.composite([{input: path + 'logo.png', gravity: 'southeast' }])
.toFile(path + 'output.png');
If you would like to center the image being overlayed:
gravity: 'centre'