I have documented all three games with screenshots through multiple playthroughs. These screenshots are there for anyone to use for whatever you'd like! Wallpapers, photoedits, icons, whatever. However, please realize that I have spent hundreds of hours creating these galleries, so when you use my screenshots, credit in the form of a linkback, preferably to the main screenshot collection, is very highly appreciated. Please don't claim the screenshots as your own. Thank you!

All screenshots are posted to my Flickr, in multiple sets, in the Mass Effect collection.

HIGH QUALITY WITH HIGH RES TEXTURE AND FLYCAM SCREENSHOTS:
All of the screenshots below were taken with a good graphics card, many .ini modifications and using texmod with high quality texture replacers. Flycam also enabled for MANY great flycam shots of every major area of the game. Femshep Paragon Kaidan Romance. See sidebar on each for details on the texmods used. These screenshots are what I reccomend you browse first, as they look the best and have flycam. However, they are not tagged.
* Mass Effect 1 - HIGH QUALITY Texture & Flycam
* Mass Effect 2 - HIGH QUALITY Texture & Flycam
* Mass Effect 3 - HIGH QUALITY Texture & Flycam

EXTENSIVELY TAGGED SCREENSHOTS:
Only my original ME2 playthrough is extensively tagged. However, these screenshots are by far the worst quality, from when I had a video card not able to really handle ME2 well. If you just want to easily find a screenshot that's NOT very good quality (very jagged shadows and lines), look here:
The ME2 Tagged album
OR
Click here to browse by tags
Click here to search by multitags (recommended)
Here is an alphabetized screenshotted list of all tags for easier browsing
OR
Here's a selection of what I consider the "Best" screenshots I have uploaded. (Tagged "Best") from that gallery and maybe one or two others

THE OTHER MASS EFFECT SCREENSHOT GALLERIES:
These galleries are not extensively tagged. Most are just tagged "Mass Effect" and you'll need to browse to find what you're looking for, sorry!

* Misc. ME2 Playthroughs, untagged, normal quality - This gallery contains other ME2 playthroughs I did, some have better graphics quality than the Tagged gallery. All of the DLCs that are not in the main gallery can be found here. There are screenshots from a Male Paragon Liaramance, A FemShep Renegade Jacobmance, and a FemShep Renegade Garrusmance.

* ME3 Demo and Trailer Screenshots - Default FemShep with Kaidan alive, plus Default MShep with Ashley alive, from the Demo PLUS screnshots from the cinematic trailer.

* Mass Effect 1 Normal Texture - Mass Effect 1 Gallery of a speedrun of a FemShep Paragon Kaidan Romance, good graphics quality.

* Mass Effect 3 Normal texture - This gallery contains Mass Effect 3 Screenshots, good quality, of my FemShep Paragon Kaidan romance (Everyone possibly alive except Kelly shows up), and also my Female Renegade Garrus Romance, Ashley alive Femshep that made MANY different choices including betraying Wreav and Paddok Wiks, Major Kirrahe killed by Kai Leng. Both original cut and extended cut screenshots can be found here, all 3 colors of ending.

* Mass Effect Edits - Sometimes I like to use my own screenshots to make edits for tumblr or whatever. As these are reworked, edited screenshots CREDIT IS REQUIRED IF YOU REPOST THESE ANYWHERE. A link to either the set or the main collection page is fine. Thank you!

After finding a screenshot you'd like to keep, click the "Actions" button above it, then "View All Sizes", then select a size up to "Original" which is quite large. You can then download the screenshot from there. Feel free to add comments, and if you see anything mistagged please just comment so I can fix it.

(Again) These screenshots are there for anyone to use for whatever you'd like! Wallpapers, photoedits, icons, whatever. However, please realize that I have spent hundreds of hours creating these galleries, so when you use my screenshots, credit in the form of a linkback, preferably to the main screenshot collection, is very highly appreciated. Please don't claim the screenshots as your own. Thank you!