GDP per capita. Used as an example for add_images_as_xlabels which does what it suggests.

GDP_per_capita.R

library(rvest)

## GDP per capita, top 10 countries
url      <- "https://en.wikipedia.org/wiki/List_of_countries_by_GDP_(nominal)_per_capita"
html     <- read_html(url)
gdppc    <- html_table(html_nodes(html, "table")[3])[[1]][1:10,]

## clean up; remove non-ASCII and perform type conversions
gdppc$Country <- gsub("Â ", "", gdppc$Country)
gdppc$Rank    <- iconv(gdppc$Rank,    "latin1", "ASCII", sub="")
gdppc$Country <- iconv(gdppc$Country, "latin1", "ASCII", sub="")
gdppc$`US$`   <- as.integer(sub(",", "", gdppc$`US$`))

## flag images (yes, this processing could be done neater, I'm sure)
## get the 200px versions
flags_img  <- html_nodes(html_nodes(html, "table")[3][[1]], "img")[1:10]
flags_url  <- paste0('http://', sub('[0-9]*px', '200px', sub('\\".*$', '', sub('^.*src=\\"//', '', flags_img))))
flags_name <- sub('.*(Flag_of)', '\\1', flags_url)

if(!dir.exists("flags")) dir.create("flags")
for(flag in seq_along(flags_url)) {
  switch(Sys.info()[['sysname']],
         Windows= {download.file(flags_url[flag], destfile=file.path("flags", paste0(flag,"_", flags_name[flag])), method="auto", mode="wb")},
         Linux  = {download.file(flags_url[flag], destfile=file.path("flags", paste0(flag,"_", flags_name[flag])))},
         Darwin = {print("Not tested on Mac. Use one of the above and find out?")})
}

library(EBImage)  ## readImage
library(dplyr)    ## %>%
library(ggplot2)  ## devtools::install_github("hadley/ggplot2)
library(grid)     ## rasterGrob
library(ggthemes) ## theme_minimal
library(scales)   ## comma

## create a dummy dataset
npoints <- length(flags_name)
y       <- gdppc$`US$`
x       <- seq(npoints)
dat     <- data.frame(x=factor(x), y=y)

## load the images from filenames
## one day I'll remember to make these sorted on save
pics       <- vector(mode="list", length=npoints)
image.file <- dir("flags", full.names=TRUE)
image.file <- image.file[order(as.integer(sub("_.*", "", sub("flags/", "", image.file))))]

## save the images into a list
for(i in 1:npoints) {
  pics[[i]] <- EBImage::readImage(image.file[i])
}

## create the graph, as per normal
## NB: #85bb65 is the color of money in the USA apparently.
gg <- ggplot(dat, aes(x=x, y=y/1e3L, group=1)) 
gg <- gg + geom_bar(col="black", fill="#85bb65", stat="identity")
gg <- gg + scale_x_discrete()
gg <- gg + theme_minimal()
gg <- gg + theme(plot.margin = unit(c(0.5,0.5,5,0.5), "lines"),
                 axis.text.x = element_blank(),
                 axis.text.y = element_text(size=14))
gg <- gg + scale_fill_discrete(guide=FALSE)
gg <- gg + theme(plot.background = element_rect(fill="grey90"))
gg <- gg + labs(title="GDP per Capita", subtitle=paste0("Top 10 countries\n(", url, ")"), x="", y="$US/1000")
gg

## insert imags (pics) as x-axis labels
## well, at least appear to do so
gg %>% add_images_as_xlabels(pics)