Anybody can put "masterpiece" in their tags to make a good image. To make a good image great is in tastefully picking the tags that aren't always optimal. Here's a selection of tags that can make a big difference.
Border
Viewfinder
polaroid photo, Fake photograph
Camera
Fisheye
Panorama
Depth of field
foreshortening - An object pointing towards the viewer made "shorter" than it really is.
blurry foreground
blurry background
Camera Angle
Dutch angle - An image that is framed at a tilted angle.
From above
Vanishing point - When the perspective of a picture appears to draw the viewer's eye towards a central point.
Perspective - An image that greatly emphasizes the three-dimensional aspects of the subject.
From outside
Upper body
Cowboy shot - Face through thighs
Wide shot, very wide shot
Lighting
Volumetric lighting
Backlighting, Sidelighting, Underlighting
Lens flare, heavy lens flare, Diffraction spikes
Atmospheric perspective
Chiaroscuro - Strong contrasts between light and dark across an entire composition.
Dappled sunlight, tree shadow
Vignetting - The image softly darkening around the edges.
Sunbeam, Light rays
crack of light
light particles
-Silhouette
-Backlighting
-Grayscale - Saturation boost
-muted color
Lighting State
Sunset
Twilight
Stage lights - Basically frontal lighting.
Embers
Candlelight
Window shadow
Colored shadow
Stylization
Abstract
Abstract Background
Surreal
Silhouette
Minimalism
Double exposure
Woven hatching - Woven hatching is a shading technique where the artist uses short sets of parallel marks in one direction. The effect looks woven or like a basket.
Pointilism - Artwork made up entirely - or almost entirely - out of dots.
Stippling - A shading technique, where shadow is applied using dots of varying density
Painterly
Spot color
colorful
lineart
graffiti art
Background
Scenery, landscape, nature, mountains
Seascape
Architecture
Cityscape, urban, skyline, rooftop
Ruins
Loaded interior, messy room
Sky focus, cloud focus
bokeh - A photographic effect where circular out-of-focus points of light appear in the background of the image.
Reflection
Posing
Pose, dynamic pose, dancing
Fighting stance
Motion blur, speed lines, motion lines, trembling
Flowing hair
hair spread out, hair flowing over
double v
heart hand duo
double thumbs up
planted sword
head tilt
semireclining position
crossed_legs_(sitting)
Image Forms
Isometric
Partially underwater shot, caustics, refraction
Comic, multiple views, cut-in, collage
fine art parody
Poster
Magazine Cover (seems the highest quality "cover" variant)
official_wallpaper, ratio:16:9, ratio:9:16
Thanks to Danbooru for the borrowed tag definitions.