Throughout City 17, the Resistance have sprayed graffiti and posters as a protest to the Combine regime. This '''imagery''' is often used to relay information, or show the player a cache point (cache points are normally signified by a Lambda logo). The images sometimes refer to existing stories and artwork, such as the "Orange and Lemons" graffiti below. In addition, the Caste graffiti shows the obvious system of oppression and dystopia in City 17. Like the Combine imagery|imagery used by the Combine, Resistance imagery can be quite abstract, and its intended message can be quite subtle.
The Lambda logo is arguably the most important and prominent Resistance logo, being the symbol for the entire Resistance movement itself. It is often used to signify Resistance supply caches or bases, and is also used in combination with other images in other pieces of graffiti.
FileResistanceLambda.jpg|Rebel with Lambda armband.
FileLambdaCacheCanals.jpg|An example of a Resistance weapons cache location signified by the logo.
FileDecalgraffiti037a.png|Lambda in a graffiti.
The 'evolution' graffiti is a common example of Resistance imagery, found in ''Half-Life 2'' and ''Episode One''. It depicts three stages of human evolution, with the first being a Homonidae, the second being a Homo Sapien Sapien, and the third being a transhumance Combine soldier. The graffiti alludes to the Combine's tampering with the process of evolution, and the loss of humanity in the transformation of a regular human into a Combine soldier.
FileDecalgraffiti056a.png|Graffiti demonstrating human evolution affected by the Combine occupation of Earth.
FileEp1 c17 050030.jpg|Ditto, in-game.
FileGraffiti evolution complete.jpg|The same graffiti with captions, from a t-shirt previously available at The Valve Store.
The 'Caste' graffiti is found sprayed near Black Mesa East and other places (such as Matt's home), depicting a Combine (or possibly Resistance, or even a recycled Conscript) soldier holding a baby next to the word 'Caste'. It may be a reference to the dystopian novel ''WikipediaBrave New World|Brave New World''. It could also hint at the social hierarchy in City 17, with citizens at the bottom, Civil Protection higher above, and the transhuman Overwatch at the top of the human 'caste system.'
FileDecalgraffiti009a.png|An example of the "Caste" graffiti near Black Mesa East.
==Oranges and Lemons==
A piece of Resistance graffiti, and an obvious reference to the nursery rhyme ''WikipediaOranges and Lemons|Oranges and Lemons'', featured in George Orwell's ''WikipediaNineteen Eighty-Four|Nineteen Eighty-Four''. The text says "WikipediaDey|DEY" in Russian.
FileDecalgraffiti062a.png|An example of the 'Oranges and Lemons' graffiti.
==Man with Umbrella Graffiti==
A piece of Resistance graffiti depicting a man standing in the rain, holding an umbrella. The image is one of the most ambiguous pieces of Resistance graffiti in terms of its meaning; one possible interpretation is that it represents humanity standing under the 'downpour of oppression'.http//webcache.googleusercontent.com/search?q=cacheJMrM1EMD0XEJforums.steampowered.com/forums/archive/index.php/t-3111797.html+&cd=1&hl=en&ct=clnk&gl=pl ''Half-Life 2'' - Imagery thread on the Steam Users' Forums (archived) It could also be a possible reference to the G-Man, as the man in the image bears certain similarities with him.
FileDecalgraffiti038a.png|Man with umbrella.
A piece of Resistance graffiti, found in ''Half-Life 2'', depicting a human hand reaching up with a lambda logo in its palm. The word 'born.' is written directly underneath. This could be a possible reference to the suppression field put in place by the Combine, preventing humans from reproducing, and thus preventing children from being born. It could also be referring to the uniqueness of humans from the Combine; humans are naturally 'born,' unlike most of the Combine's units which are formed artificially.
FileDecalgraffiti024a.png|"Born" poster, with the Lambda logo in a hand.
The 'Resist' graffiti depicts Wallace Breen|Breen's likeness with the word 'resist' written underneath. Sometimes the latter is not present.
FileDecalgraffiti003a.png|An example of the 'Resist' graffiti.
A piece of graffiti depicting the equation for the WikipediaElectrical resistance and conductance|electrical resistance. The letter 'A' is circumscribed - the same symbol is used by the WikipediaAnarchy|anarchy movement.
FileDecalgraffiti046a.png|An example graffiti with the equation.