So I tried my textures (the ones I've been tinkering with making which worked fine on a new world in 0.4) on a world that was created in 0.3.1 and all the new graphics aren't added due to the following errors:
4:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_brick.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_furnace_front.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_furnace_side.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_grass.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_junglegrass.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_leaves.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_stone.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_stone.png^gemstones_emerald_stone.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_stone.png^gemstones_ruby_stone.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_stone.png^gemstones_sapphire_stone.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_stone.png^mineral_coal.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_stone.png^mineral_iron.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_tree.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_tree_top.png" because image is large
04:26:18: INFO[main]: TextureSource::buildMainAtlas(): Not adding "default_wood.png" because image is large
I presume this is maybe some incompatibility created by copying over an older world to the newer version but not sure.
Each of those images average about 10-30KB. The gemstones are much much smaller. Like less than a KB generally.