FeaturePlot from Seurat: change its title
I tried with some data that I have and this is working for me: 

p &lt;- FeaturePlot(object = seurat_object, features.plot = id, cols.use = c("grey", "blue"),
                      reduction.use = "tsne", do.return = TRUE)


lapply(p, function(x){x + labs(title = endothelial_symbols[1])})


I think it is because FeaturePlot returns several ggplot objects according to the ids you put. This is returned as a list of plots so you have to iterate each one for labeling.