Presentation

Does every graphic have a purpose?
Is every graphic comprehensible (informative title, axis labels, caption, or legend?)
If using statistical summaries, can you still see the actual data? If not, do you have a good reason?
If using statistical summaries, are appropriate measures of uncertainty included?
Are color palettes intuitive? (eg blue = cold, red = hot)
Does “more mean more”? (eg larger size or deeper hue maps to the larger value of the variable)
Is meaning of graphical elements consistent across small multiples?
Are any changes in design driven by the data?
Does the presentation have a clear intro, middle, and end?
Is there a coherent story?
Does all interactivity or animation show something that you couldn’t show with a static graph?
Does any interactivity or animation hinder rather than help?

Paper

Have all comments from milestone reviews been addressed?
Have all grammatical errors and other typos been fixed?
Are ggplot themes consistent throughout?
Are all titles, labels, etc. readable? Do any run off the page?
(all graphic items from the presentation section should also be followed)
Are warnings and messages from R hidden in your final knitted file?
Do graphics appear in the correct order, near the text where they are referred to?
Is your paper formatted nicely?
Do you have a reference list (or footnotes) that is nicely formatted?

VisCheck Simulate how your images look for people with different forms of colorblindness (web-based)

Adobe Color: Create, share, and explore rule-based and custom color palettes.
viridis Perceptually uniform color scales (I use these often!)
ColorBrewer Sequential, diverging, and qualitative color palettes that take accessibility into account.

Google Fonts Free, well-made fonts that you can download to your computer and use
Ultimate Google Font Pairings A list of well-designed font pairings that are available on Google Fonts.