Eurographics EuroGlobalMap is a potential datasource "1:1 million scale topographic dataset covering 45 countries and territories in the European region"
Detail level / quality
First impression, judging by the sample image, the data set is too coarse detail to be of any use in improving OpenStreetMap's european data coverage. We already have superior coverage throughout Europe.
Open Data. They require attribution.
Maybe listing them on the Contributors page would be enough to satisfy this requirement (as it has been for other data providers) but we would need to check if we were to use the dataset.